Revert "WifiManager: Retrieve IWifiManager service lazily"

Couple of reverts in the CL:
a) Revert "WifiManager: Return dummy values when wifi service is not up"
This reverts commit dfb747ef.
b) Revert "WifiManager: Retrieve IWifiManager service lazily"
This reverts commit 2161b39d.

Reason for revert: Wifi services no longer plan to be a separate
APK/process for mainline. Will instead become a jar loaded from Apex.

Bug: 144722612
Test: Device boots up & connects to wifi networks.
Change-Id: Ic0bd8392f3c8e85b72dd62460c540e8cf58fc705