Remove warning "find_preferred_connection: no connection and !create"

Remove warning "find_preferred_connection: no connection and !create"

find_preferred_connection() is called with !create via
afs_ConnByHost->afs_ConnBySA to determine if there is a cached
connection available.  Don't warn, as it will next be called with the
create flag to create the connection anyway.

Change-Id: I02c2150a04ef20c54da793926fb402b946311f9a
Reviewed-on: https://gerrit.openafs.org/12964
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>