adb: Add persistent system property for running adb in TCPIP mode

In addition to service.adb.tcp.port, you can now set persist.adb.tcp.port
to specify the port number for adb to listen to instead of USB.
This allows the adb TCP configuration to persist across reboots.

Change-Id: I897ffcb019e8dd1785996d2f3c571cfc2f8ded38
Signed-off-by: Mike Lockwood <lockwood@android.com>