FS: Fix lazy initialization of non-volatile static field

FS: Fix lazy initialization of non-volatile static field

The 'factory' field is lazy initialized in the detect() method.

According to FindBugs:

   Because the compiler or processor may reorder instructions, threads
   are not guaranteed to see a completely initialized object, if the
   method can be called by multiple threads.

Fix this by declaring the member as 'volatile'.

Change-Id: Ib32663bb28c9564584256e01f625b4e7875e6223
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>