Use 'top' instead of 'sleep' as a dummy command

Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>

tests/unit/config_test.py

@@ -348,12 +348,12 @@ class ExtendsTest(unittest.TestCase):
             {
                 'name': 'mydb',
                 'image': 'busybox',
-                'command': 'sleep 300',
+                'command': 'top',
             },
             {
                 'name': 'myweb',
                 'image': 'busybox',
-                'command': 'sleep 300',
+                'command': 'top',
                 'links': ['mydb:db'],
                 'environment': {
                     "FOO": "1",

tests/unit/container_test.py

@@ -14,7 +14,7 @@ class ContainerTest(unittest.TestCase):
         self.container_dict = {
             "Id": "abc",
             "Image": "busybox:latest",
-            "Command": "sleep 300",
+            "Command": "top",
             "Created": 1387384730,
             "Status": "Up 8 seconds",
             "Ports": None,