SoftapController: support for Fast Session Transfer

To support Fast Session Transfer (FST), hostapd needs to
run with global control interface. Added optional support
to run it with global control interface with default
behaving as in existing functionality.

FST manager needs to run before hostapd starting running,
to achieve this calls to prepare for soft AP mode was added.

Change-Id: Ib552de30c7c200f46f08b72c819dba160bce8eba