samba: check AD membership with net

Seems more reliable than adcli. Not sure how reliable any of this
actually is.

roles/samba/tasks/main.yml

@@ -28,7 +28,7 @@
     line: session optional pam_mkhomedir.so
 
 - name: Check domain membership
-  command: 'adcli testjoin -D {{ domain }}'
+  command: 'net ads testjoin'
   changed_when: false
   failed_when: false
   register: ad_join