Fix invalid requests imports introduced in #4604.

Even when we remove the requests controller the pyc files will stick around - so probably best to keep these absolute imports for these controllers indefinitely. This broke workflow import from URL coming through the GUI and so it broke a bunch of Selenium tests.

lib/galaxy/webapps/galaxy/controllers/async.py

@@ -2,6 +2,8 @@
 Upload class
 """
 
+from __future__ import absolute_import
+
 import logging
 import urllib
 

lib/galaxy/webapps/galaxy/controllers/library_common.py

@@ -1,3 +1,5 @@
+from __future__ import absolute_import
+
 import glob
 import json
 import logging

lib/galaxy/webapps/galaxy/controllers/root.py

@@ -1,6 +1,8 @@
 """
 Contains the main interface in the Universe class
 """
+from __future__ import absolute_import
+
 import cgi
 import os
 

lib/galaxy/webapps/galaxy/controllers/workflow.py

@@ -1,3 +1,5 @@
+from __future__ import absolute_import
+
 import base64
 import httplib
 import json