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/052 b/tests/qemu-iotests/052
index 4d4e411..6bdae92 100755
--- a/tests/qemu-iotests/052
+++ b/tests/qemu-iotests/052
@@ -39,7 +39,7 @@
 . ./common.filter
 
 _supported_fmt generic
-_supported_proto generic
+_supported_proto file
 _supported_os Linux
 _default_cache_mode "writethrough"
 _supported_cache_modes "writethrough"