Panic when receiving Cloud without IPAM provider

[jduepmeier]

Describe the bug

If the cloud configuration does not define an ipam provider a panic occurs.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x1741002]
 
goroutine 1 [running]:
github.com/vmware/load-balancer-and-ingress-services-for-kubernetes/ako-infra/avirest.AviCloudCachePopulate(0x0?, {0x1b83ff7, 0xd})
        /build/mts/release/bora-21883866/cayman_load-balancer-and-ingress-services-for-kubernetes/build/release/lin64/load-balancer-and-ingress-services-for-kubernetes/build/src/ako-infra/avirest/handle_netinfo.go:398 +0x3c2
github.com/vmware/load-balancer-and-ingress-services-for-kubernetes/ako-infra/avirest.getAviCloudFromCache(...)
        /build/mts/release/bora-21883866/cayman_load-balancer-and-ingress-services-for-kubernetes/build/release/lin64/load-balancer-and-ingress-services-for-kubernetes/build/src/ako-infra/avirest/handle_netinfo.go:345
github.com/vmware/load-balancer-and-ingress-services-for-kubernetes/ako-infra/avirest.SyncLSLRNetwork()
        /build/mts/release/bora-21883866/cayman_load-balancer-and-ingress-services-for-kubernetes/build/release/lin64/load-balancer-and-ingress-services-for-kubernetes/build/src/ako-infra/avirest/handle_netinfo.go:51 +0x110
main.InitializeAKOInfra()
        /build/mts/release/bora-21883866/cayman_load-balancer-and-ingress-services-for-kubernetes/build/release/lin64/load-balancer-and-ingress-services-for-kubernetes/build/src/cmd/infra-main/main.go:114 +0x86a
main.main()
        /build/mts/release/bora-21883866/cayman_load-balancer-and-ingress-services-for-kubernetes/build/release/lin64/load-balancer-and-ingress-services-for-kubernetes/build/src/cmd/infra-main/main.go:39 +0x17

Reproduction steps

1. Setup a cloud without IPAM provider
2. Run ako pod
3. Panic occurs

Expected behavior

No panic should occur.

Additional context

I think the problem is this line: https://github.com/vmware/load-balancer-and-ingress-services-for-kubernetes/blob/master/ako-infra/avirest/handle_netinfo.go#L399

It deferences the CloudCache.IPAMProviderRef without checking for nil.

[akshayhavile]

@jduepmeier Thanks. We will look into it.