GUI - 1264, 1265 When creating a new security group, if the VPC option is changed, remove...

... the previoisly added rules since now the security groups are specific to VPCs

https://eucalyptus.atlassian.net/browse/GUI-1264
https://eucalyptus.atlassian.net/browse/GUI-1265
@kyolee310, don't we still need resetValues() here, or is clearRules() enough in this block?