When in offline/message only, while Pure is in message poll mode and
incoming call will happen CellularService will start answering call thus
resulting to show the incorrect info in call log and not showing the
first call after Online mode is switched back.
This commit is cherry-picked from EGD-7332.
It implements mode Offline Messages only - connecting to
the GSM network in defined by user intervals and rejecting
incomig calls during connected phase. It also implements
handling of connetion interval setiing and small fix in modes
popup.
