Fix bug in MPTiff storage class. The finish() method should not return (and thus indicate that data is finished) until all pending writing tasks have completed--images and ImageJ and OME metadata. With this fix, finish() now works correctly, blocking until the writing executor terminates. Failing to do so leaves open the possibility of closing to FileChannel prior to writing completion.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14756 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd