[nemo-qml-plugin-email] Run next offline action when in offline mode and  current action is online.

When in offline mode, if current action requires network, we try to
run all offline action in the queue in the meantime.
Well consider this:
0. No actions running
1. Phone offline
2. Call an online action
-> It will be set as current action, but it won't get executed
3. Call another online action
-> It will be set as new current action, and the previous action will be lost!