Use the buffer engine for elm tests

This should make tests work also on jenkins

tests/elementary/test_01_basics.py

@@ -1,5 +1,8 @@
 #!/usr/bin/env python
 
+import os
+os.environ["ELM_ENGINE"] = "buffer"
+
 import unittest
 import logging
 

tests/elementary/test_02_image_icon.py

@@ -1,6 +1,8 @@
 #!/usr/bin/env python
 
 import os
+os.environ["ELM_ENGINE"] = "buffer"
+
 import unittest
 import logging
 

tests/elementary/test_03_entry.py

@@ -1,6 +1,9 @@
 #!/usr/bin/env python
 # encoding: utf-8
 
+import os
+os.environ["ELM_ENGINE"] = "buffer"
+
 import unittest
 import logging
 

tests/elementary/test_04_external.py

@@ -1,6 +1,9 @@
 #!/usr/bin/env python
 
-import os, unittest
+import os
+os.environ["ELM_ENGINE"] = "buffer"
+
+import unittest
 import logging
 
 from efl import evas

tests/eo/test_02_class_names.py

@@ -1,5 +1,8 @@
 #!/usr/bin/env python
 
+import os
+os.environ["ELM_ENGINE"] = "buffer"
+
 from efl import evas
 from efl import edje
 from efl import emotion