Fix tests for Java 6.

 - Change the guava version used to match the one included in the SDK.
   The test server uses the same. However, the command line build still
   uses the guava present at platform/external/guava, which is compiled
   with Java 7. Thus, running the tests from inside the IDE can be done
   via Java 6.
 - Rebuilt the test app classes with Java 6 compatibility.
 - Change similarity threshold to prevent differences due to some locale
   settings different java versions.

Change-Id: Ic71d43256a8cf6f9df296e63550667a202c7105f