SUNRPC: Fix default hostname created in rpc_create()

Since 43780b87..., rpc_create() fills in a default hostname based on
the ip address if the servername passed in is null.  A small typo made
that default incorrect.  (But this information appears to be used only
for debugging right now, so I don't believe the typo causes any bugs in
the current kernel.)

Thanks to Olga Kornievskaia for bug report and testing.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Olga Kornievskaia <aglo@citi.umich.edu>
Cc: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>