adb: fix the initial adbd state in AdbService

AdbService::systemReady used to set mIsAdbUsbEnabled
and mIsAdbWifiEnabled without starting adbd
explicitly. In the rest of the file these variables
means that adbd is already started and writing
to these variables without starting adbd breaks
the invariant.

mIsAdbUsbEnabled and mIsAdbWifiEnabled will be set
through AdbSettingsObserver in setAdbEnabled.
mDebuggingManager.setAdbEnabled will also be
called there.

Bug: 402444824
Test: * flashed a user build into Pixel 9a
      * enabled USB debugging
      * ran `adb shell getprop ro.build.fingerprint`
      * rebooted Pixel 9a
      * ran `adb shell getprop ro.build.fingerprint`
Flag: EXEMPT cleanup
Change-Id: I449c3c5f364860c3d6bae86f973f59eba5920139
Signed-off-by: Roman Kiryanov <rkir@google.com>