Add floating IP QoS test cases

This patch adds test cases for neutron bp/floating-ip-rate-limit.
We will create a server with one floating IP. And attach qos
bandwidth rules to the floating IP. Then try to download data
from the server to calculate the bandwidth whether is under
the qos limit.

Depends-On: Ibef48e7842a276fe77c901403d67760871f2b7e0
Partially-Implements blueprint: floating-ip-rate-limit

Change-Id: I50d1775cd1f86201bd21d24650f2c52f316ef1b8
diff --git a/neutron_tempest_plugin/scenario/constants.py b/neutron_tempest_plugin/scenario/constants.py
index 258c587..ddd45ff 100644
--- a/neutron_tempest_plugin/scenario/constants.py
+++ b/neutron_tempest_plugin/scenario/constants.py
@@ -15,4 +15,5 @@
 SERVER_STATUS_ACTIVE = 'ACTIVE'
 DEFAULT_SECURITY_GROUP = 'default'
 LIMIT_KILO_BITS_PER_SECOND = 1000
+LIMIT_KILO_BYTES = 1000
 SOCKET_CONNECT_TIMEOUT = 60