unittests: remember to use AM_LDFLAGS
unittests: remember to use AM_LDFLAGS

remember to use AM_LDFLAGS when setting _LDFLAGS. Otherwise, the global
flags will be lost.

Signed-off-by: Colin McCabe <7b35906f1d014e74a9dc8c913eb229119df647aa@dreamhost.com>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph