storage: Add comment to picking return value of qemu-img

Commit d7b2679253504d6defa9fc7159b572cfd6a25a95 introduced
a return value picking of qemu-img on '-h', but without any comment.

diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
index c8e19c8a8c2fa2c41582115c48e663f751d918da..b423d110fc979a30e0f670ca770eaba1e4538878 100644 (file)
--- a/src/storage/storage_backend.c
+++ b/src/storage/storage_backend.c
@@ -628,6 +628,9 @@ static int virStorageBackendQEMUImgBackingFormat(const char *qemuimg)
     virCommandSetOutputBuffer(cmd, &help);
     virCommandClearCaps(cmd);
 
+    /* qemuimg doesn't return zero exit status on -h,
+     * therefore we need to provide pointer for storing
+     * exit status, although we don't parse it any later */
     if (virCommandRun(cmd, &exitstatus) < 0)
         goto cleanup;