wifi: check if supplicant is running before starting it

Wrong property was used to check if wpa_supplicant was running.
Fix this

Change-Id: I6a5bd7a3acae84f5ba4bba317d04191e0e59b2e7
Author: Jonathan DE CESCO <jonathan.de.cesco@intel.com>
Signed-off-by: Jonathan DE CESCO <jonathan.de.cesco@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 66748