Add comment to function validateExistingPV[C] functions #995

Job	Run time
Golangci Lint	28s
Linters	1m 51s
drenv tests (3.9)	1m 51s
drenv tests (3.10)	2m 1s
drenv tests (3.11)	1m 38s
Unit tests	8m 54s
Build image	6m 34s
ramenctl tests (3.9)	17s
ramenctl tests (3.10)	33s
ramenctl tests (3.11)	19s
Check artifacts and operator deployment (1.20.7)	3m 47s
Publish built image	1m 47s
	30m 0s

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