Bug: RedisCache can be Provisioned and FailedProvisioning

[babbageclunk]

Describe the bug
We've had reports of RedisCache being in the state Provisioned=true, FailedProvisioning=true.
From reading the code this can happen because it initially failed (possibly a temporary error that we aren't checking for), and then on a subsequent periodic reconciliation the ARM query reported that it was deployed successfully. The code that updates the state to Provisioned=true doesn't unset FailedProvisioning.

To Reproduce
Steps to reproduce the behavior:

• Deploy a RedisCache and hit a transient (but unknown to us) error
• The cache will be marked as failed
• Wait for the error to go away and the cache to be reconciled
• The cache will be marked as Provisioned=true, FailedProvisioning=true

Expected behavior
Ideally the transient error should be recognised so that the cache stays in provisioning until it passes, but at the least when it goes to provisioned the failed provisioning flag should be unset.