shell: Get address of Docker machine from the right place

Fixes #1217
Closes #1268
Reviewed-by: Stef Walter <stefw@redhat.com>
daemon: Always set mount point and options of block

So that removal of configuration items is correctly reflected.

Fixes #1158
Closes #1269
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Clear storage dialogs on enter

Fixes #1218
Closes #1271
Reviewed-by: Stef Walter <stefw@redhat.com>
polkit: Tweak policy to work for Cockpit.

By installing our own rules.
daemon: Run usermod via pkexec.

So that admins can change roles and password hashes of user accounts.
daemon: Perform systemd actions via pkexec and systemctl.

Instead of via D-Bus methods.  This enables admins to start/stop/etc
services.
test: Run more tests as "admin".

Fixes #1203
Fixes #1204
Fixes #1206