Staging: lustre: Fix Space Requirement around ':' in conrpc.c

The patch fixes the following checkpatch.pl error in conrpc.c-
ERROR: spaces required around that ':'

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>