auth, rgw, common: switch to PK11_ImportSymKey_FIPS wrapper.

auth, rgw, common: switch to PK11_ImportSymKey_FIPS wrapper.

PK11_ImportSymKey() is a part of NSS API that becomes unavailable
in the FIPS mode. Apparently NSS targets stricter restrictions
than those coming from Level 1 of FIPS 140-2. In the consequence,
loading a symmetric key from plain keyring or key db (which Ceph
needs to do due to architectural reasons) fails.

The same issue affected corosync and this patchset deals with it
the same way like already followed by corosync [1]:
a raw crypto key is in-memory wrapped with fresh, random wrapping
key just before being imported via PK11_UnwrapSymKey(). Of course,
this effectively lowers to FIPS level 1. Still, this would be no
different from what OpenSSL (to which we are currently migrating
in master) gives in the matter.

The patch can be *roughly* verified in following steps:
  1. mkdir ./nssdb
  2. certutil -N -d ./nssdb --empty-password
  3. modutil -dbdir ./nssdb -fips true
  4. ../src/vstart.sh -l -n -b -o "nss_db_path=/work/ceph-3/build/nssdb"

This fix is dedicated to Luminous. In master we're switching to OpenSSL.

[1] 5dadebd21862074deaeb9a337fc9e49f5e9f692a in corosync's public repo.

Fixes: http://tracker.ceph.com/issues/38843
Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>