Update condition to select right pvc as child for statefulset (#550)

* Update if condition to select right pvc as child for statefulset

Signed-off-by: hanzala <muhammad.hanzala@waltlabs.io>

* fix indentation

Signed-off-by: hanzala <muhammad.hanzala@waltlabs.io>

* test(cache): Add tests for isStatefulSetChild function

* test(pkg/cache): Replace JSON unmarshalling with structured approach in tests

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Signed-off-by: hanzala <muhammad.hanzala@waltlabs.io>
Co-authored-by: hanzala <muhammad.hanzala@waltlabs.io>
Co-authored-by: Obinna Odirionye <odirionye@gmail.com>