Telephony no sporadic call indicators

First commit fixes erroneous suppression of hold indicators with unchanged data; hold indicators need to be output even if their value stays the same.

Second commit makes sure call status indicator is output only once when primary and secondary call are both manipulated; adjusted the existing mechanism for suppressing extra hold indicators slightly to fit both purposes. Ofono would send one signal for each call state transition; code would previously send call status indicators for both, which causes problems.