Merge branch 'fix-broken-new-project-import' into 'master'

Fix OAuth2 issue importing a new project from GitHub and GitLab

It appears that the GitLab OAuth2 client options were converted to strings instead of symbols when merged with the default options (i.e. `{}.merge(github_options)`). As a result, the OAuth2 defaults were being used. For example, the OAuth2 client options would have a key with `authorize_url` and `:authorize_url`, but the former was never used. As a result, the OAuth2 client would always use the wrong URL to talk to GitHub.

Note that this bug should also have affected GitLab, but not Bitbucket: The OAuth client is careful to convert all keys to symbols.

Closes #1268

See merge request !425

lib/gitlab/github_import/client.rb

@@ -46,7 +46,7 @@ module Gitlab
       end
 
       def github_options
-        OmniAuth::Strategies::GitHub.default_options[:client_options].dup
+        OmniAuth::Strategies::GitHub.default_options[:client_options].symbolize_keys
       end
     end
   end