Fix -Wno-format and -Werror=format-security options clash

Fix -Wno-format and -Werror=format-security options clash

This causes build failure in latest fedora builds, ceph_test_librbd_fsx adds -Wno-format cflag but the default AM_CFLAGS already contain -Werror=format-security, in previous releases, this was tolerated but in the latest fedora rawhide it no longer is, ceph_test_librbd_fsx builds fine without -Wno-format on x86_64 so there is likely no need for the flag anymore

Signed-off-by: Boris Ranto <branto@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>