pam: include pam_keyinit.so in our PAM fragments

We want that systemd --user gets its own keyring as usual, even if the
barebones PAM snippet we ship upstream is used. If we don't do this we get the
basic keyring systemd --system sets up for us.

src/login/systemd-user.m4

@@ -3,10 +3,10 @@
 # Used by systemd --user instances.
 
 account required pam_unix.so
-
 m4_ifdef(`HAVE_SELINUX',
-session  required pam_selinux.so close
-session  required pam_selinux.so nottys open
+session required pam_selinux.so close
+session required pam_selinux.so nottys open
 )m4_dnl
-session  required pam_loginuid.so
+session required pam_loginuid.so
+session optional pam_keyinit.so force revoke
 session optional pam_systemd.so