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 master in 1 minute and 35 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Test
passed #486811
build_dev

00:01:32

passed #486810
build_stable

00:01:17