Improve initialization sequence for supplicant

AIDL VTS tests.

Bug: 215298798
Bug: 215467859
Test: atest VtsHalWifiSupplicantStaIfaceTargetTest \
            VtsHalWifiSupplicantStaNetworkTargetTest \
            VtsHalWifiSupplicantP2pIfaceTargetTest
      (Tested on both a Coral and Oriole device)
Change-Id: I435e16a447af16d9cd619c5bc8883ed24151080a