Add NO_VERSION to avoid rebuilding ceph_ver.h and relinking

Signed-off-by: Dan Mick <dan.mick@inktank.com>
Makefile-env.am, Makefile.am: move secret.c out of libcommon

ceph.mount and rbd.cc now include secret.c as part of their objects,
and KEYUTILS_LIB is a dependency only for those files.

Signed-off-by: Dan Mick <dan.mick@inktank.com>