pam: Fix rhost check when rhost is unavailable

Don't exit early if the rhost field isn't filled in, as it usually isn't
for a lot of services.

Fixes: 3274a311
2 jobs for wip/hadess/fix-no-ssh-pam in 1 minute and 46 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #486228
build_dev

00:01:46

passed #486227
build_stable

00:01:28