[gnome-control-center] (16 commits) ...tests: Add VPN related tests

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

Summary of changes:

  a51dbcd... network: Fix Bluetooth panel showing up after connection re (*)
  52034ba... network: Update VPN title when the connection is changed (*)
  77a1225... network: Fix disconnecting the VPN connection_removed_cb ha (*)
  3950e66... tests: Unset wayland display environment variable correctly (*)
  f3322b4... tests: Do not show_all the network panel (*)
  7c43f95... tests: Add trivial test to check empty network panel (*)
  77edec5... tests: Allow creating VPNs in the NM test service (*)
  b14e514... tests: Improve helpers to wait for NM events (*)
  bfdd2e0... tests: Use the same NMClient as the panel (*)
  edc85ab... tests: Return NMRemoteConnection from add_cb (*)
  4f3aec7... tests: Add delete_cb for network panel testing (*)
  ab59a8f... tests: Use g_assert_nonnull rather than testing for != NULL (*)
  d45512d... tests: Check that Bluetooth section is not shown (*)
  12555d6... tests: Add helper to find a parent widget to network test (*)
  870b64b... tests: Also wait for ConnectionAdded signal from NetworkMan (*)
  e1e82cc... tests: Add VPN related tests (*)

(*) This commit already existed in another branch; no separate mail sent