In several places we run 'gnome-terminal' explicitly, but as of
today's compose, the default terminal app on GNOME in Rawhide is
ptyxis, not gnome-terminal.
Running 'terminal' should launch whichever is correct, so let's
consistently do that.
Also, add an apps_run_terminal needle for ptyxis.
Signed-off-by: Adam Williamson <awilliam@redhat.com>
