In preparation to possible automatic regression and performance
testing for the block layer I found that the iotests don't work
for all protocols anymore.

In commit 1f7bf7d0 I started to change supported protocols from
generic to file for various tests. Unfortunately, some tests
added in the meantime again carry generic protocol altough they
can only work with file because they require local file access.

The other way around for some tests that only support file I added
NFS protocol after confirming they work.
Signed-off-by: NPeter Lieven <pl@kamp.de>
Reviewed-by: NBenoît Canet <benoit.canet@nodalink.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>