Update redis version to avoid celery crash

Latest redis 3.0.1 version is not compatiable with celery,
lock the version to 2.10.6 for now.

Celery have updated with:
celery/celery#5175

not release yet.

Signed-off-by: Wayne Sun <gsun@redhat.com>

Pipfile

@@ -26,7 +26,7 @@ kombu = "*"
 kerberos = "*"
 "ldap3" = "*"
 pytz = "*"
-redis = "*"
+redis = "==2.10.6"
 requests = "*"
 coloredlogs = "*"
 "psycopg2-binary" = "*"