Check for mtu setting in neutron package
Add setup for default external interface
Fix MTU to be applied to external and default interfaces

If you define external or default interfaces via
the CLI, apply them to the setup.sh script, and
apply MTU to only those interfaces defined via
the CLI.
fix error in here script for mtu_fix
externa_interface ==> external_interface
Check for default interface IP Address
Merge pull request #4 from onecloud/fix_mtu_and_external_interface

Fix mtu and external interface