ceph: do not configure external metric endpoint is not present
ceph: do not configure external metric endpoint is not present

If no endpoint are configured let's simply return.

Closes: https://github.com/rook/rook/issues/7963
Signed-off-by: Sébastien Han <62d754cc350e84d3b1c32ae79f976f5348e74a40@redhat.com>

rook/rook,rook/rook,rook/rook,rook/rook,rook/nfs,rook/rook,rook/nfs,rook/nfs