Allow UsbDeviceManager to start adbd again.

There's some weird state where if persist.sys.usb.config=none,adb, then
adbd won't get started. Give back adbd start permissions to
UsbDeviceManager to see if that fixes the issue.

Bug: 150130503
Bug: 150116813

Test: adb shell su 0 setprop persist.sys.usb.config none,adb; adb reboot
adb should be online after.

Change-Id: I36c6ef4b20d58570a2d51ed70088ae5c54d6687d
Exempt-From-Owner-Approval: Fix adbd offline failure
(cherry picked from commit 7a3800993d)

core/java/android/debug/AdbManagerInternal.java

@@ -53,4 +53,14 @@ public abstract class AdbManagerInternal {
      * Returns the file that contains all of the ADB keys and their last used time.
      */
     public abstract File getAdbTempKeysFile();
+
+    /**
+     * Starts adbd for a transport.
+     */
+    public abstract void startAdbdForTransport(byte transportType);
+
+    /**
+     * Stops adbd for a transport.
+     */
+    public abstract void stopAdbdForTransport(byte transportType);
 }