Another session handling fix

The previous session handling fix introduced a problem where a
newly installed copy of the app would return a null value when
checking for the session token of a connection.
Fixed DatabaseHandler to add a default empty string for the column
and to add a check to return an empty string instead of a null
value.

Change-Id: I6fb8184bb3420f5a88658bdc50be59c543c9fc49
Work around SDP setting race condition causing NPE

If the VM responds too quickly with it's answer SDP, it could trigger a
race condition in which drainRemoteCandidates gets called twice when it
is meant to only ever be called once. After draining the candidates
from the queue, the queue itself is nulled out, so a second call to drain
would throw a null pointer exception. Added a null check to drain as a
workaround. The race still exists, but should be harmless for now.

Change-Id: I9a56bf03b165371caab64a6145706c2d3796035f
Disable obnoxiously noisy logging

We really don't need to log every time we send a message up to the VM.

Change-Id: I35c22ac6b3a468f703f7e13e7b0f794203ba73d6