libxtreemfs (java): add bugfix and tests for Issue #277

Issue #277 was a bug in the java libxtreemfs in the offset translation from file
offsets to object offsets when using Filehandle.read(). The offset calculation
was erroneous for nonaligned (i.e. offset % blocksize != 0) offsets greater than
Integer.MAX_VALUE. The error was found to be a pair of missing braces in the
StripeTranslatorRaid0.translateReadRequest().
The commit fixes the bug and adds regressiontests against it.