Change defaults for last membership timestamp updates on groups and stems

The defaults for the following properties are changing from true to false. Most people don't care about these properties anymore since there's auditing. And it looks like LDAPPCNG may stop using these in 2.1 (see GRP-696).

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1. 1. Settings to track last membership changes for groups and stems.
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1. If true, when an immediate membership changes for a group (either a privilege or a list member),
2. then an update will be made to the lastImmediateMembershipChange property for the group.
   groups.updateLastImmediateMembershipTime = false

1. If true, when an immediate, composite, or effective membership changes for a group (either a privilege or a list member),
2. then an update will be made to the lastMembershipChange property for the group.
   groups.updateLastMembershipTime = false

1. If true, when an immediate or effective membership changes for a stem (this would be a naming privilege),
2. then an update will be made to the lastMembershipChange property for the stem.
   stems.updateLastMembershipTime = false