Cluster creation fails when no resource pool is specified

[srm09]

/kind bug

What steps did you take and what happened:

• Enable the node anti affinity feature for the CAPV deployment
• Create a cluster with the KCP and the MD objects using VSphereMachineTemplate objects without a resource pool, set VSPHERE_RESOURCE_POOL to ''
• Cluster creation fails since the VSphereCluster object never moves to Ready state.

What did you expect to happen:

• Cluster creation should succeed since resource pool is an optional field for VSphereMachineTemplate CR.

Anything else you would like to add:
Similar to the clone operation, if no resource pool is specified, then the resource pool lookup should fallback to the default value.

Environment:

• Cluster-api-provider-vsphere version: v1.4.0