[core] Incremental analysis mixes XPath rule violations
**Affects PMD Version:** 6.17

**Rule:** TooManyStaticImports (but maybe the problem is not related to the rule)

**Description:**
I updated my Gradle version to 5.6 and started to use incremental analysis flag.
https://docs.gradle.org/5.6/release-notes.html#support-for-pmd-incremental-analysis
It seems that the rule reference is wrong but the description is right.
Also the priority field is from the wrong rule.
Here 2 example of xml. Unfortunately I can't give you my project to test this issue, sorry.


**Code Sample demonstrating the issue:**
**right example**
```
<?xml version="1.0" encoding="UTF-8"?>
<pmd xmlns="http://pmd.sourceforge.net/report/2.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://pmd.sourceforge.net/report/2.0.0 http://pmd.sourceforge.net/report_2_0_0.xsd"
    version="6.17.0" timestamp="2019-08-26T11:46:19.393">
<file name="MyFile.java">
<violation beginline="1" endline="457" begincolumn="1" endcolumn="2" rule="TooManyStaticImports" ruleset="Code Style" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_codestyle.html#toomanystaticimports" priority="5">
Too many static imports may lead to messy code
</violation>
</file>
</pmd>
```
**wrong example**
```
<?xml version="1.0" encoding="UTF-8"?>
<pmd xmlns="http://pmd.sourceforge.net/report/2.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://pmd.sourceforge.net/report/2.0.0 http://pmd.sourceforge.net/report_2_0_0.xsd"
    version="6.17.0" timestamp="2019-08-26T10:35:33.313">
<file name="MyFile.java">
<violation beginline="1" endline="457" begincolumn="1" endcolumn="2" rule="ByteInstantiation" ruleset="Performance" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_performance.html#byteinstantiation" priority="2">
Too many static imports may lead to messy code
</violation>
<violation beginline="1" endline="457" begincolumn="1" endcolumn="2" rule="ByteInstantiation" ruleset="Performance" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_performance.html#byteinstantiation" priority="2">
Too many static imports may lead to messy code
</violation>
<violation beginline="1" endline="457" begincolumn="1" endcolumn="2" rule="ByteInstantiation" ruleset="Performance" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_performance.html#byteinstantiation" priority="2">
Too many static imports may lead to messy code
</violation>
<violation beginline="1" endline="457" begincolumn="1" endcolumn="2" rule="ByteInstantiation" ruleset="Performance" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_performance.html#byteinstantiation" priority="2">
Too many static imports may lead to messy code
</violation>
</file>
</pmd>
```
I also executed pmd different times:
**first launch**
```
<file name="MyFile.java">
<violation beginline="1" endline="442" begincolumn="1" endcolumn="2" rule="ByteInstantiation" ruleset="Performance" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_performance.html#byteinstantiation" priority="2">
Too many static imports may lead to messy code
</violation>
```
**second launch**
```
<file name="MyFile.java">
<violation beginline="1" endline="457" begincolumn="1" endcolumn="2" rule="ProperCloneImplementation" ruleset="Error Prone" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_errorprone.html#propercloneimplementation" priority="2">
Too many static imports may lead to messy code
</violation>
```
**third launch after clean**
```
<file name="MyFile.java">
<violation beginline="1" endline="457" begincolumn="1" endcolumn="2" rule="JUnitStaticSuite" ruleset="Error Prone" package="my.package" class="MyFile" externalInfoUrl="https://pmd.github.io/pmd-6.17.0/pmd_rules_java_errorprone.html#junitstaticsuite" priority="3">
Too many static imports may lead to messy code
</violation>
```
**fourth launch after clean**
rule reference changed again: **WhileLoopWithLiteralBoolean**

**Running PMD through:** Gradle 5.6

O.S. both linux and windows
JDK 1.8