gui: clear the sensitive cache between two event runs

Was causing a SIGSEGV.

Related to rhbz#1069917

Signed-off-by: Jakub Filak <jfilak@redhat.com>
gui: don't remove already removed GTimeoutSource

Was causing a GLib warning

Related to rhbz#1069917

Signed-off-by: Jakub Filak <jfilak@redhat.com>
gui: reload destroyed sensitive data warn widgets from the galde

clear_warnings() destroys the warning widgets. The sensitive data
widgets needs to be reloaded as GtkBuilder does not return clones of
object but the instances from its cache.

Related to rhbz#1069917

Signed-off-by: Jakub Filak <jfilak@redhat.com>
gui: add "Repeat" button

If an event run fails, the button allows users to modify the
configuration and re-run the event.

v2:
- add a help text explaining what to do before clicking "Repeat" button

Related to rhbz#1069917

Signed-off-by: Jakub Filak <jfilak@redhat.com>