Unable to update status

[kshamajain99]

Is this a BUG REPORT or FEATURE REQUEST?:
Bug

What happened:
IAM policy was updated by adding a forbidden policy. But, status was not updated to PolicyNotAllowed. Instead controller was returning following error

2020-09-25T00:23:35.892Z	ERROR	controllers.iamrole_controller.UpdateStatus	Unable to update status	{"request_id": "41e0254d-a604-41e6-a6c4-13e6cc81850f", "status": "PolicyNotAllowed", "error": "Iamrole.iammanager.keikoproj.io \"iamrole\" is invalid: status.lastUpdatedTimestamp: Invalid value: \"null\": status.lastUpdatedTimestamp in body must be of type string: \"null\""}
github.com/go-logr/zapr.(*zapLogger).Error
	/go/pkg/mod/github.com/go-logr/[email protected]/zapr.go:128
github.com/keikoproj/iam-manager/controllers.(*IamroleReconciler).UpdateStatus
	/workspace/controllers/iamrole_controller.go:360
github.com/keikoproj/iam-manager/controllers.(*IamroleReconciler).HandleReconcile
	/workspace/controllers/iamrole_controller.go:144
github.com/keikoproj/iam-manager/controllers.(*IamroleReconciler).Reconcile
	/workspace/controllers/iamrole_controller.go:98
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler
	/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:256
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem
	/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:232
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).worker
	/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:211
k8s.io/apimachinery/pkg/util/wait.JitterUntil.func1
	/go/pkg/mod/k8s.io/[email protected]/pkg/util/wait/wait.go:152
k8s.io/apimachinery/pkg/util/wait.JitterUntil
	/go/pkg/mod/k8s.io/[email protected]/pkg/util/wait/wait.go:153
k8s.io/apimachinery/pkg/util/wait.Until
	/go/pkg/mod/k8s.io/[email protected]/pkg/util/wait/wait.go:88```

**What you expected to happen**:
CR status should have updated to PolicyNotAllowed

**Environment**:
- iam-manager version
- Kubernetes version :

$ kubectl version -o yaml

[kshamajain99]

similar to prometheus-operator/prometheus-operator#2399

kubernetes/kubernetes#86811

[kshamajain99]

Temporary fix has been made by #60.