qemu: Remove /dev mount info properly

Just so it doesn't bite us in the future, even though it's unlikely.

And fix the comment above it as well.  Commit e08ee7cd took the
info from the function it's calling, but that was lie itself in the
first place.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

src/qemu/qemu_domain.c

@@ -226,11 +226,10 @@ qemuDomainGetPreservedMounts(virQEMUDriverPtr driver,
         return 0;
     }
 
-    /* Okay, this is crazy. But virFileGetMountSubtree() fetched us all the
-     * mount points under /dev including /dev itself. Fortunately, the paths
-     * are sorted based on their length so we skip the first one (/dev) as it
-     * is handled differently anyway. */
-    VIR_DELETE_ELEMENT(mounts, 0, nmounts);
+    /* Since the list is sorted and only has paths that start with /dev, the
+     * /dev itself can only be first. */
+    if (STREQ(mounts[0], "/dev"))
+        VIR_DELETE_ELEMENT(mounts, 0, nmounts);
 
     if (VIR_ALLOC_N(paths, nmounts) < 0)
         goto error;