mount-setup: relabel items mentioned directly in relabel-extra.d

relabel_extra() relabels the descendants of directories listed in
relabel-extra.d, but doesn't relabel the files or directories
explicitly named there.  This makes it impossible to use
relabel-extra.d to relabel the root of a filesystem.  Fix by
relabeling the named items too.

src/core/mount-setup.c

@@ -486,6 +486,7 @@ static int relabel_extra(void) {
                         }
 
                         log_debug("Relabelling additional file/directory '%s'.", line);
+                        (void) label_fix(line, 0);
                         (void) nftw(line, nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
                         c++;
                 }