Provider id is not set correctly when using PowerVSMachineProviderConfig.ServiceInstance

[Karthik-K-N]

When the machine is created by supplying ServiceInstance.ID or Name, The machine provider id the serviceinstance will be empty

For example:
Expected format: ibmpowervs://region/zone/service_instance_id/powervs_machine_id
Actual format: ibmpowervs://region/zone//powervs_machine_id

Add a check to validate non empty service instance id before forming a ProviderID

Reference:

machine-api-provider-powervs/pkg/actuators/machine/reconciler.go

Line 214 in 0bd184d

providerID := client.FormatProviderID(r.powerVSClient.GetRegion(), r.powerVSClient.GetZone(), r.providerSpec.ServiceInstanceID, *instance.PvmInstanceID)