hfp: Synchronize call state in case of +CHUP error

hfp: Synchronize call state in case of +CHUP error

It is possible for the phone to accept Dial request
but not actually dial. This leaves a voicecall object
in state 'dialling' that cannot be removed.
Proposed workaround is to trigger AT+CLCC when an error
is returned for Hangup. As the call is not on the list,
this would remove this hanging object and signal CallRemoved.

Windows Phone trace with this fix:
ofonod[273]: > ATD1;\r
ofonod[273]: < \r\nOK\r\n
ofonod[273]: src/voicecall.c:dial_handle_result() Registering new call: 1
ofonod[273]: < \r\n+CIEV: 5,4\r\n
ofonod[273]: src/network.c:ofono_netreg_strength_notify() strength 80
ofonod[273]: > AT+CHUP\r
ofonod[273]: < \r\nERROR\r\n
ofonod[273]: src/voicecall.c:generic_callback() command failed with error: Unknown error type
ofonod[273]: > AT+CLCC\r
ofonod[273]: < \r\nOK\r\n
ofonod[273]: src/voicecall.c:ofono_voicecall_disconnected() Got disconnection event for id: 1, reason: 2