For OVS based DPDK ports ingress bandwidth limit is now implemented
using egress-policer qos type.
Additionally limit values are set in other_config of QoS because there
is no queue used in this case.
This patch moves also helper methods used to conversion between
bytes and bits and between bits and kilobits to neutron.common.utils
to be able to use it also in ovs_lib module.
Change-Id: I94d1e8dfb82df5c602476db8aaa884ae91fecd7f
Closes-Bug: #1724729