EUCA-5609:source security group in loadbalancer

Source security group is returned in describe-load-balancer response.
Users can configure the rule so that the group for backend instances accept traffic from the loadbalancer's source group
EUCA-5611: create keypairs for loadbalancer VMs
This is to help sysadmin debugging the loadbalancer Vms.
New euca property, loadbalancer_vm_keyname, is used to specify the keyname to be associated with the loadbalancer VMs when launched.

EUCA-5641: replace '.' with different character in LB name.
Currently the LB name is used as part of the DNS name of the LB. The fix is to avoid unintended '.' in the DNS name.
Also, the fix includes restricting the name of loadbalancer something that could be a hostname.
Merge branch 'dev/spark/services' into testing