Rename standby methods

ThreadBase::standby() returns the value of mStandby.

RecordThread::standby() "overrode" ThreadBase::standby(), but with a
different meaning and no return value.  This meant you couldn't
access the parent's class definition within RecordThread.

This could be confusing, so this CL renames RecordThread::standby()
to standbyIfNotAlreadyInStandby().

Change-Id: I9196ee12701dd2dccdfaed922af2d7b8e8774676