crypto: allow PK11 module to load even if it's already initialized

crypto: allow PK11 module to load even if it's already initialized

there is chance that other pieces of application loads PK11 module
already and does not finalize it before calling common_init_finish().

also, upon fork, PK11 module resets its entire status including `nsc_init`,
by which PK11 module tell if it is initialized or not. so the behavior
of NSS_InitContext() could be different before and after fork. that's
another reason to ignore CKR_CRYPTOKI_ALREADY_INITIALIZED error (see
NSS_GetError()).

Fixes: http://tracker.ceph.com/issues/19741
Signed-off-by: Kefu Chai <kchai@redhat.com>