Reliably wait for Synaptic's search button to fade in.

Apparently an earlier simplification of this step removed some
confusing code that actually made this wait reliable. However, by
requiring and exact match we achieve the same in a clearer manner.
Make image less prone to false positive matches by Sikuli.

It seems the old image sometimes matched the search button in
Synaptic's main window.
Remove workaround for showing the TBB's menu bar (Closes #8028).

In the end it seems the TBB will keep on hiding the menu bar, so we
use the menu button instead.
Merge branch 'feature/8028-remove-unsafe-browser-test-menu-workaround' into feature/jessie

Conflicts:
	features/step_definitions/unsafe_browser.rb
Merge remote-tracking branch 'origin/feature/jessie' into feature/jessie
Wait for Pidgin's "connecting" status more reliably.

... by closing the accounts window, which otherwise may block parts of
the Pidgin status area. At least in Jessie.
Update some test suite images vs Jessie.
Stack another workaround on #8271.

Unfortunately the workaround in commit 992cc82 breaks the "Tails seems
to have booted normally" step if "GNOME has started" (with the
workaround) has run before. That breaks, for instance, the "Tails can
boot from live systems stored on hard drives" in
untrusted_partitions.feature.

Just to be extra clear: this definitely is a temporary workaround.
Merge remote-tracking branch 'origin/feature/jessie' into feature/jessie