[minor] Allow Mongodb update to use already configured storageclass

[racree]

When "mas update" is run, mongodb community update needs to respect the existing storage class and not change it.

[racree]

To test this pull request, I deployed MAS using catalog v8-231004-amd64 and specified custom storage class of "custom-ceph-rbd". I then ran "mas update" and chose the v8-231128-amd64 catalog. The comparison of MongoDBCommunity CRs shows mongodb version was upgraded from 4.4.21 to 5.0.21 and the storageClassName correctly remained the same "custom-ceph-rbd"

And "mas update" was successful.

[racree]

I also tested this by running mas install with the v8-231004-amd64 catalog and subsequently running "mas update" and specifying the v8-231031-amd64 catalog. As shown below, the MongoDBCommunity CR version remained 4.4.21 and the storageClassName correctly remained "custom-ceph-rbd"

mas update was successful.

[racree]

NOTE: This PR does not depend on any code changes in ansible-devops.