python-common/ceph/smb: add client.py for remote-control grpc client
Add a new client.py that contains the main library for acting as a
client of the remote-control grpc service for SMB. This is based on grpc
reflection rather than rigidly following an api generated from protobuf.
As this system is rapidly evolving this avoids having to keep generated
files in sync and more closely matches the grpcurl tool people are
already using with this feature.
Signed-off-by: John Mulligan <jmulligan@redhat.com>