iotests: Drop vpc from 004's and 104's format list

Both tests require the test image to have a specific size; this cannot
be guaranteed by vpc (unless tuning the test specifically for that
format).

It is safe to exclude vpc from 004 because what is tested there is
implemented in a generic part in the block layer and not
format-specific.

It is safe to exclude vpc from 104 because for vpc basically every image
size is "unaligned", so if that would break at some point in time, we
would quickly notice just by running the generic tests.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/004

@@ -38,7 +38,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.rc
 . ./common.filter
 
-_supported_fmt generic
+_supported_fmt raw qcow qcow2 qed vdi vmdk vhdx
 _supported_proto generic
 _supported_os Linux
 

tests/qemu-iotests/104

@@ -34,7 +34,7 @@ trap "exit \$status" 0 1 2 3 15
 . ./common.rc
 . ./common.filter
 
-_supported_fmt generic
+_supported_fmt raw qcow qcow2 qed vdi vmdk vhdx
 _supported_proto generic
 _supported_os Linux