In dual station case, wlan0 is connected to AP, wlan1
connects to the same ap and will get failed because two
interfaces can not connect to same band (same ap).
At present wlan1 will do unlink bss of ap after connect fail.
This may corrupt the bss tree in kernel because the bss is
still pointed by wlan0’s wdev -> current_bss.
Fix by avoid the unlink bss if the bss is still connected
in any interfaces.
Change-Id: I27c76eca2d4f130addabbdc2600f6959d24c8511
CRs-Fixed: 2837496
d4b3e3d043