Add exponential gap to retry decorator
Add exponential gap to retry decorator

This sets the retry interval to 100 ms and turns on the
inc_retry_interval flag which doubles the interval on each
failure to our standard retry decorator. This avoids exhausting
all of the retries in a very short window.

With our MAX_RETRIES set to 10, this means it will sleep a cumulative
time of about 8 seconds if all retry attempts fail.

Change-Id: Ife01e8e5444b035cf797e3d575c6799f92a021a5

igor-toga/local-snat,sebrandon1/neutron,openstack/neutron,eayunstack/neutron,mahak/neutron,noironetworks/neutron,mahak/neutron,openstack/neutron,huntxu/neutron,noironetworks/neutron,igor-toga/local-snat,mahak/neutron,huntxu/neutron,eayunstack/neutron,cloudbase/neutron,openstack/neutron,cloudbase/neutron,sebrandon1/neutron