Change status query into a information message when finishing a rolling restage - main

[ccjaimes]

This change will prevent the issue reported in Jira's ticket CLI-50 which creates a race condition when trying to query the app's rolling restage status at the same moment the old restage group gets deleted.

Link for v8: #2664
Link for v7: #2665

[ccjaimes]

Self review, no critical change in logic, LGTM

[a-b]

The change looks ok, please add tests. Here is an example Expect(testUI.Out).To(Say("Staging app and tracing logs..."))

[pivotalgeorge]

as this change was made to resolve a tricky-to-reproduce issue, going to document the setup here:

• used a TAS 4.0 testing environment, set up such that the compute bosh job (which hosts garden and therefore app instances) was on a GCP VM with 32GB memory, 131GB root disk, and 2vCPUs
• used a version of the cf-cli built off the v8 branch - specifically c7d46b6
• 10 sample apps, each using the dora code but named dora-1, dora-2, etc.
• 3-at-a-time restaging of those apps, i.e. cf restage "dora-$i" --strategy rolling --no-wait & for i := {1,2,3}, followed by the next 3, etc.
• observed Process not found FAILED, etc.
• rotating too many (all 10) apps at a time also resulted in Process not found, but this was a red herring as it was caused by InsufficientResources (out of memory)
• observed that the same testing procedure did not result in an error using a version of the binary built from this PR (d444bc1)