Add print_function import

As in PY2 and PY3 we have different result after calling
print, add print_function import to have the same behaviour
when using empty print.

Change-Id: I59c644d196805bb8a2592fc84a839c7a75d78f1a

cinderclient/shell_utils.py

@@ -12,6 +12,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from __future__ import print_function
+
 import sys
 import time