Improved: Fix some bugs SpotBugs reports (OFBIZ-12386)

  After https://gitbox.apache.org/repos/asf?p=ofbiz-framework.git;h=33fc03fa10

  I thought the problem was fixed since it's excluded. But it was not because
  there was a typo (a trailing blank in
  <Bug pattern="SING_SINGLETON_HAS_NONPRIVATE_CONSTRUCTOR " />)

  So I fixed that, but to my surprise it still does not work, weird :/

Completes previous commit. The reason was that the whole class was concerned.

spotbugs/exclude.xml

@@ -193,9 +193,8 @@ under the License.
     <Bug pattern="EQ_CHECK_FOR_OPERAND_NOT_COMPATIBLE_WITH_THIS" />
   </Match><!-- ^ ^ not a problem, false positives -->
   <Match>
-    <!-- As it's also used by WebAppCacheTest class I made it package. That's safer but not enough as private so it's here -->
+    <!-- As it's also used by WebAppCacheTest class I made it package. That's safer but not enough as private so it's here with the whole class-->
     <Class name="org.apache.ofbiz.webapp.WebAppCache" />
-    <Method name="WebAppCache" />
     <Bug pattern="SING_SINGLETON_HAS_NONPRIVATE_CONSTRUCTOR" />
   </Match>
 </FindBugsFilter>