Fix for adb shell hang after adb root.

Abort JDWP thread if netstate is shutting down.

Bug 4731499

Change-Id: I4e1ec9cf64d00682b1dd10e448c3665a4fc77ba8
diff --git a/vm/jdwp/JdwpAdb.cpp b/vm/jdwp/JdwpAdb.cpp
index 84abe3a..ccda1f4 100644
--- a/vm/jdwp/JdwpAdb.cpp
+++ b/vm/jdwp/JdwpAdb.cpp
@@ -270,6 +270,9 @@
             sleep_ms += (sleep_ms >> 1);
             if (sleep_ms > sleep_max_ms)
                 sleep_ms = sleep_max_ms;
+
+            if (netState->shuttingDown)
+                return false;
         }
     }