ALLJOYN-1866 Release bus attachment after test is complete.

Change-Id: Ia28864fa5d8c392901b69ac7ace9601ab65c70a8
ALLJOYN-1697 Messages from proximity scanner were too frequent

The proximity scanner had few debug statements that were output
to logcat in release mode. This caused too many debug statements
to be generated. The statements were originally added for the
test team to make it easier for them to spot certain aspects of
the scanner
MarshalStressTest.tearDown now finalizes busAttachments

Change-Id: I5a039631ed22322bfc4dfb6f11d5c7ff416ba50e