lockd: change nlmclnt_grant() to take a "struct sockaddr *"

Adjust the signature and callers of nlmclnt_grant() to pass a "struct
sockaddr *" instead of a "struct sockaddr_in *" in order to support IPv6
addresses.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>