Cellular: Cannot use private "_is_connected" flag.

[mudassar-ublox]

In cellular api's _is_connected flag is private and is used in do_connect function and do_connect is virtual. How child classes can use this flag, _is_connected. when do_connect is overridden child classes.

Also when do_connect is overridden then we cannot set this flag, _is_connected . So while calling do_disconnect because of _is_connected this check become true and sets _cid = -1 and when deactivate_context function is called give error. It will be better to add some method to set _is_connected.

[INFO][CELL]: AT TX (11): AT+CGACT=0,
[INFO][CELL]: AT TX ( 2): -1
[INFO][CELL]: AT TX ( 1):
[INFO][CELL]: AT RX ( 9): ERROR

Issue request type

[ ] Question
[ ] Enhancement
[x] Bug

[mudassar-ublox]

@wajahat-ublox @fahim-ublox

[0xc0170]

cc @ARMmbed/mbed-os-wan

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1854

[kivaisan]

@ARMmbed/mbed-os-maintainers , I think this issue can be closed. Fix has been merged a long time ago.