CLOUDSTACK-1604: deploy VM failed when global setting "vm.allocation.algorithm" is set to "userdispersing"

Changes:
- DeployPlannerSelector was newly introduced for BareMetal feature. It had the planner name hardcoded.
- Change it to decide the planner by referring to the global config vm.allocation.algorithm value
Summary: security_group.py: catch exception when flushing chain

Detail: Added exception handling around iptables chain flushing, along
with a call to default_network_rules() to re-initialize.

Testing:
On agent, ls /var/run/cloud and pick one of the VMs to test with. Make a
backup of it's logfile (eg cp /var/run/cloud/i-2-1722.log /tmp )
Destroy the firewall ruleset for that VM with
/usr/lib64/cloud/common/scripts/vm/network/security_group.py destroy_network_rules_for_vm --vmname i-2-1722-VM --vif vnet10
Now copy the log file back, edit the file and decrement the last field by 1
ACS should notice the out-of-date sequence ID and push a new ruleset for
the VM within 60 seconds.

BUG-ID: CLOUDSTACK-1685
Bugfix-for: John Kinsella
Reviewed-by:
Reported-by:
Signed-off-by: John Kinsella <jlk@stratosec.co> 1363286927 -0700
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-cloudstack