btrfs-progs: tests: fix mkfs/025 detection of zoned support

When 'nullb setup' fails to detect something, e.g. the null_blk module,
the whole test fails though the failure is supposed to be caught and
test not run. Use the correct helper that handles potential failures.

Signed-off-by: David Sterba <dsterba@suse.com>

tests/mkfs-tests/025-zoned-parallel/test.sh

@@ -22,7 +22,7 @@ count=10
 declare -a devices
 declare -a names
 
-run_check $SUDO_HELPER "$nullb" setup
+run_mayfail $SUDO_HELPER "$nullb" setup
 if [ $? != 0 ]; then
 	_not_run "cannot setup nullb environment for zoned devices"
 fi