qemu-iotests: change _supported_proto to file for various tests

all these tests do anything of the following and thus fail with any
protocol other than file:
 - the tests use rm, cp or mv shell commands which only work on file
 - the tests use qcow2.py
 - the images construct new filenames (e.g. backing file names) and
   the logic is broken for anything else than file

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/tests/qemu-iotests/013 b/tests/qemu-iotests/013
index 389f4b8..ea3cab9 100755
--- a/tests/qemu-iotests/013
+++ b/tests/qemu-iotests/013
@@ -41,7 +41,7 @@
 
 # much of this could be generic for any format supporting compression.
 _supported_fmt qcow qcow2
-_supported_proto generic
+_supported_proto file
 _supported_os Linux
 
 TEST_OFFSETS="0 4294967296"