Don't unregister hold advertising information

Don't unregister hold advertising information

[Problem] Restarted advertising triggered by LE connection request
 doesn't have the information about sender and handle. It causes some
 malfunctions (e.g. Connect LE to out-of-range LE device twice. The
 second one is requested as Directed Advertising (Slave role request))
[Cause & Measure] Advertising information is flushed once it is stopped
 by LE connection request. So even though it is restarted by hold
 advertising logic, there is no sender / advertising handle information.
 It causes the next time hold advertising failed.
 This patch doesn't unregister hold state advertising slot. Because it
 will be used again after timer is expired. Or, once timer is cancelled,
 it will be unregistered properly.
[Checking Method] Connect LE to out-of-range LE device twice

Change-Id: Ia79dd8ab5ba06778d946856883879c1f5a93d898