Use a global lock for all HDF5 Tables calls

See https://trac.openmicroscopy.org.uk/ome/ticket/10464
Add lock to HdfStorage in unit tests
Revert "Exclude failing table tests from Travis"

If this doesn't fix the tests but https://trac.openmicroscopy.org.uk/ome/ticket/10464 is no longer a problem it suggests the tests need a more complex locking setup.
This reverts commit e8baad4c9ad354827342c8107f034001d2fceec9.
Pass str(path) to PyTables
Merge pull request #3 from joshmoore/hdf5_locking-5_1

Pass str(path) to PyTables
Merge pull request #2688 from manics/hdf5_locking-5_1

Use a global HDF5 lock (trac: 10464)