checkbox-touch: make saving of reports sequential

This patch makes saving of two reports sequential. Thanks to that, there is one
point of code where both reports are saved without resolving to a some form of
a barrier.

Signed-off-by: Maciej Kisielewski <maciej.kisielewski@canonical.com>
checkbox-touch: display dialog after saving reports

This patch makes Checkbox Touch show a dialog when reports are done saving.

Fixes: https://bugs.launchpad.net/checkbox-touch/+bug/1399623
Signed-off-by: Maciej Kisielewski <maciej.kisielewski@canonical.com>
"automatic merge of lp:~kissiel/checkbox/fix-1399623/ by tarmac [r=zkrynicki][bug=1399623][author=kissiel]"