fix: ignore errors when vpc does not have default security groups

[michaelhtm]

Issue #2661

Description of changes: Currently the controller has been returning an error if the VPC securityGroup is not found. With this change, we will ignore errors if we can't find the security group

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This pull-request has been approved by: michaelhtm

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@michaelhtm: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ec2-verify-code-gen	887d501a248d99c2b1c5ba694214624de00587ba	link	false	/test ec2-verify-code-gen

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