mkpamrules: Support openSUSE's usage of /usr/etc/pam.d

to contain the pam configuration files:

https://lists.opensuse.org/opensuse-factory/2019-08/msg00113.html

instfiles/pam.d/mkpamrules

@@ -8,6 +8,7 @@ outfile="$3"
 
 service="xrdp-sesman"
 pamdir="/etc/pam.d"
+pamdir_suse="/usr/etc/pam.d"
 
 guess_rules ()
 {
@@ -16,6 +17,11 @@ guess_rules ()
     return
   fi
 
+  if test -s "$pamdir_suse/common-account"; then
+    rules="suse"
+    return
+  fi
+
   if test -s "$pamdir/common-account"; then
     if grep "^@include" "$pamdir/passwd" >/dev/null 2>&1; then
       rules="debian"