Add to Null checking log in IsSameEowner

Add to Null checking log in IsSameEowner

When building with MULTIPLE_OWNER=1, ace is updated as appending alwadys,
because the return value is false in IsSameEowner in case both ewoner1 and
ewoner 2 are NULL.

Change-Id: I0068db4196fb467e4c95d29ae808848d95776bbe
Signed-off-by: js126.lee <js126.lee@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/14891
Reviewed-by: Chul Lee <chuls.lee@samsung.com>
Reviewed-by: Jongmin Choi <jminl.choi@samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>