[FIXED JENKINS-45786] Add readResolve() to VSphereCloudRetentionStrategy

[balleman]

to ensure super.idleMinutes is properly restored from persistent state

[pjdarton]

Thanks for doing this - it's much appreciated.
My personal workload has been such that I've not been able to look at & test the build that was produced from this PR yet, but I hope to finish that interruption off tomorrow and then I'll be able to test the resulting plugin and merge it if it all works as expected.
If you hear nothing by the end of this week, feel free to nag me :-)

[pjdarton]

OK, this looks good to me - it fixes the problem I was trying to solve with #78 but with far less code changes. I'll close #78 and merge this one.