Add timeout to lock in MtpServer configure

In situations where MtpServer is in a bad state, this will prevent
the configure call from blocking indefinitely, which will prevent
a few visible problems and allow the state to recover on the next
config change.

Bug: 34873000
Test: Connect to AA test sled
Change-Id: I5daf9cfcec69c967bde6bf3f6fd90e1c434e18bb
diff --git a/media/mtp/MtpFfsHandle.h b/media/mtp/MtpFfsHandle.h
index b4d5a97..7491a1b 100644
--- a/media/mtp/MtpFfsHandle.h
+++ b/media/mtp/MtpFfsHandle.h
@@ -36,7 +36,7 @@
 
     bool mPtp;
 
-    std::mutex mLock;
+    std::timed_mutex mLock;
 
     android::base::unique_fd mControl;
     // "in" from the host's perspective => sink for mtp server