[git] IDEA-103375 Fix understanding Git submodule roots

Git submodule repository is located not in submodule/.git, but
in supermodule/modules/.git.
At the same time submodule/.git is a file which contains the path to
the real repository location.
We already detect this, but we didn't use refresh to search for the
root as a VirtualFile, and in most cases it was not in the VFS yet.

plugins/git4idea/src/git4idea/GitUtil.java

@@ -143,7 +143,7 @@ public class GitUtil {
       }
       pathToDir = FileUtil.toSystemIndependentName(canonicalPath);
     }
-    return VcsUtil.getVirtualFile(pathToDir);
+    return VcsUtil.getVirtualFileWithRefresh(new File(pathToDir));
   }
 
   /**