Fix for bug 1353044 - Core dump when creating JNI object

This problem happens during T2 multi thread testing, because the static
variable JavaMethods_ is not protected. Because of this a second thread
is accessing JavaMethods_ before the first thread finished initializing.
Fix is to add mutex to protect JavaMethods_ initialization.

Change-Id: Icc1adf143df2c36394a77f4e753a63ef64e4d08b
Merge "Fix for bug 1353044 - Core dump when creating JNI object"