SUNRPC: Clean up bc_send()

Clean up: Merge bc_send() into bc_svc_process().

Note: even thought this touches svc.c, it is a client-side change.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>