staging: lustre: lnet: Fix recent breakage from list_for_each conversion

Commit 8e55b6fd ("staging: lustre: lnet: replace list_for_each
with list_for_each_entry") was intended to be an idempotent change,
but actually broke the behavior of ksocknal_add_peer() causing mounts to fail.
The fact that it caused an existing "route2 = NULL;" to become
redundant could have been a clue.  The fact that the loop body
set the new loop variable to NULL might also have been a clue

The original code relied on "route2" being NULL if nothing was found.
The new code would always set route2 to a non-NULL value if the list
was empty, and would likely crash if the list was not empty.

Restore correct functionality by using code-flow rather the value of
"route2" to determine whether to use on old route, or to add a new one.

Fixes: 8e55b6fd

 ("staging: lustre: lnet: replace list_for_each with list_for_each_entry")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>