Refine Findbugs filters in pdftest module

QA-1153

Author: amedee

pdftest/findbugs-filter.xml

@@ -1,9 +1,16 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <FindBugsFilter>
     <Match>
+        <Class name="com.itextpdf.test.ITextTest"/>
+        <Method name="createStringByEscaped"/>
         <Bug pattern="DM_DEFAULT_ENCODING"/>
     </Match>
     <Match>
+        <Class name="com.itextpdf.test.WrappedSamplesRunner"/>
+        <Or>
+            <Method name="checkIfTestAndCreateParams"/>
+            <Method name="initClass"/>
+        </Or>
         <Bug pattern="EXS_EXCEPTION_SOFTENING_NO_CONSTRAINTS"/>
     </Match>
-</FindBugsFilter>
+</FindBugsFilter>