disable doozer/zk tests using environment variables

configdb/tests/test_db_api_doozer.py

 import os
+from nose.exc import SkipTest
 try:
     import doozer
     from doozer.client import IsDirectory, NoEntity
+    if os.getenv('SKIP_DOOZER') is not None:
+        raise SkipTest('doozer tests disabled')
 except ImportError:
-    from nose.exc import SkipTest
     raise SkipTest('doozer not found')
 
 from configdb.db.interface import doozer_interface

configdb/tests/test_db_api_zookeeper.py

 import os
+from nose.exc import SkipTest
 try:
     from configdb.db.interface import zookeeper_interface
+    if os.getenv('SKIP_ZOOKEEPER') is not None:
+        raise SkipTest('Zookeeper tests disabled')
 except ImportError:
-    from nose.exc import SkipTest
     raise SkipTest('Zookeeper not found')
 
 from configdb.tests import *

configdb/tests/test_doozer_interface.py

 import os
+from nose.exc import SkipTest
 try:
     import doozer
     from doozer.client import IsDirectory, NoEntity
+    if os.getenv('SKIP_DOOZER') is not None:
+        raise SkipTest('doozer tests disabled')
 except ImportError:
-    from nose.exc import SkipTest
     raise SkipTest('doozer not found')
 
 from configdb.db.interface import doozer_interface

configdb/tests/test_zookeeper_interface.py

 import os
+from nose.exc import SkipTest
 try:
     from configdb.db.interface import zookeeper_interface
+    if os.getenv('SKIP_ZOOKEEPER') is not None:
+        raise SkipTest('Zookeeper tests disabled')
 except ImportError:
-    from nose.exc import SkipTest
     raise SkipTest('Zookeeper not found')
 
 from configdb.tests import *