Fixed problems with unit test tripping over undefined behavior.

Fixed problems with unit test tripping over undefined behavior.

Corrected several test cases that caused crashes under glib due
to triggering undefined behavior in locked mutex clearing. Similar
prohibitions exist for pthreads also.

Added if() checks after EXPECT_TRUE cases that checked for NULL.
Without this the code will dereference null pointers when one
of the possible failure scenarios is encountered.

Change-Id: I232b52a715e7d3c0f7952756a7e98e6522b64dae
Signed-off-by: Jon A. Cruz <jonc@osg.samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/813
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Joseph Morrow <joseph.l.morrow@intel.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>