Add server prefix to utst_int.xg

Add server prefix to utst_int.xg

When compiling src/ubik/utst_int.ss.c, a warning would be produced since
the server stubs are defined as accepting an rx_connection instead of an
rx_call, and since the server and client RPC stubs have the same name.
Give a server prefix so we can distinguish between the two, and fix the
server stubs and squash the warning, similar to
bd011aeee7f5dad5c61fd81a90b296c46a0b9058.

Change-Id: Iebf843bcabb4cf8f4a56c6ac30d210573b58d801
Reviewed-on: http://gerrit.openafs.org/876
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>