Python: Fix FPs for py/import-own-module

Before I added `--max-import-depth=2`, there was a bit of trouble, where it
would alert on `from pkg_ok import foo2` -- since all the `pkg_ok.foo<n>`
modules were missing, I guess the analysis didn't make any assumptions on
whether `foo2` is a module or a regular attribute.

python/ql/src/Imports/ModuleImportsItself.ql

@@ -14,7 +14,12 @@ import python
 
 predicate modules_imports_itself(Import i, ModuleValue m) {
     i.getEnclosingModule() = m.getScope() and
-    m.importedAs(i.getAnImportedModuleName())
+    m = max(string s, ModuleValue m_ |
+            s = i.getAnImportedModuleName() and
+            m_.importedAs(s)
+        |
+            m_ order by s.length()
+        )
 }
 
 from Import i, ModuleValue m