ceph-handler: Fix radosgw_address default value

ceph-handler: Fix radosgw_address default value

The rgw restart script set the RGW_IP variable depending on ansible
variables:
  - radosgw_address
  - radosgw_address_block
  - radosgw_interface

Those variables have default values defined in ceph-defaults role:

radosgw_interface: interface
radosgw_address: 0.0.0.0
radosgw_address_block: subnet

But in the rgw restart script we always use the radosgw_address value
instead of the radosgw_interface when defined because we aren't testing
the right default value.
As a consequence, the RGW_IP variable will be set to 0.0.0.0 even if
the ip address associated to the radosgw_interface variable is set
correctly. This causes the check_rest function to fail.

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>