importer: Allow /usr/local RPM content

Obviously, this alone is not enough to expose that content but it's a
start. Currently as is, it'll get nuked when we replace `/usr/local` by
a symlink in postprocessing. A future patch will address that part.

Part of coreos#233.

rust/src/importer.rs

@@ -392,7 +392,7 @@ fn path_is_ostree_compliant(path: &str) -> bool {
         return true;
     }
 
-    if path.starts_with("/usr/") && !path.starts_with("/usr/local") {
+    if path.starts_with("/usr/") {
         return true;
     }