rgw: added rgw-policy-check

rgw: added rgw-policy-check

rgw-policy-check - a program to do syntax checking on bucket policy.
This program just reads the policy into memory, so it is not
checking anything except syntax.

Signed-off-by: Marcus Watts <mwatts@redhat.com>
rgw: Fix return value of `rgw-policy-check`

Signed-off-by: Adam C. Emerson <aemerson@redhat.com>
rgw: Use ceph initialization in `rgw-policy-check`

Specifically so we can pull in the options from `ceph.conf` and similar.

Signed-off-by: Adam C. Emerson <aemerson@redhat.com>