Add param for growth factor in devstack lib
Add param for growth factor in devstack lib

Change-Id: I00a83013bcbb308e7644ad115a6c459f5ed3622d

ed-/solum,gilbertpilz/solum,ed-/solum,devdattakulkarni/test-solum,stackforge/solum,ed-/solum,gilbertpilz/solum,openstack/solum,stackforge/solum,openstack/solum,gilbertpilz/solum,ed-/solum,devdattakulkarni/test-solum,gilbertpilz/solum