aws-custom-route-controller tries to update routes when instance is in invalid state

[ialidzhikov]

/kind bug

What happened:
We frequently see transient errors such as:

53m         Warning   RoutesUpdateFailed             serviceaccount/aws-custom-route-controller   creating route 10.101.10.0/24 -> i-<uid> in table rtb-<uid> failed: IncorrectInstanceState: Instance with state 'shutting-down' is not valid for this operation....
53m         Warning   RoutesUpdateFailed             serviceaccount/aws-custom-route-controller   creating route 10.101.10.0/24 -> i-<uid> in table rtb-<uid> failed: IncorrectInstanceState: Instance with state 'shutting-down' is not valid for this operation....
53m         Warning   RoutesUpdateFailed             serviceaccount/aws-custom-route-controller   creating route 10.101.10.0/24 -> i-<uid> in table rtb-<uid> failed: InvalidParameterValue: Invalid value 'i-<uid>' for instance ID. Instance is not in a VPC....
52m         Warning   RoutesUpdateFailed             serviceaccount/aws-custom-route-controller   creating route 10.101.10.0/24 -> i-<uid> in table rtb-<uid> failed: InvalidParameterValue: Invalid value 'i-<uid>' for instance ID. Instance is not in a VPC....
52m         Warning   RoutesUpdateFailed             serviceaccount/aws-custom-route-controller   creating route 10.101.10.0/24 -> i-<uid> in table rtb-<uid> failed: InvalidParameterValue: Invalid value 'i-<uid>' for instance ID. Instance is not in a VPC....

What you expected to happen:
If possible, aws-custom-route-controller to not try to update routes for instances in invalid states (instance is shutting-down or instance is not in VPC).

How to reproduce it (as minimally and precisely as possible):
See above.

Anything else we need to know:
N/A

Environment:
Version: v0.5.0