WARNING: eliminate warnings: [-Wsometimes-uninitialized]

WARNING: eliminate warnings: [-Wsometimes-uninitialized]

The warning is caused by decls "TWEntry* entry = NULL;" coming
after tests that call "goto exit;" where "entry" is used.
the decl in front of the conditionals removes the warning.

Also added NULL test on "entry" to avoid unecessary calls
to TWDeleteEntry.

Change-Id: I0d7069e2497563a2c5378789c26acfdd3c48d89d
Signed-off-by: Gregg Reynolds <reynolds-gregg@norc.org>
Reviewed-on: https://gerrit.iotivity.org/gerrit/8599
Reviewed-by: George Nash <george.nash@intel.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Habib Virji <habib.virji@samsung.com>