lastmodified field in VersionedModel set on creation
lastmodified field in VersionedModel set on creation

VersionedModels don't semantically change after they're created - the only
changes are to disable it.  Having lastmodified update when enabled changed
caused problems when ordering by lastmodified, since both the original and
new rule were modified within the same second.  By setting lastmodified on
creation for VersionedModels, it fixes ordering problems.

artefactual/archivematica-fpr-admin,artefactual/archivematica-fpr-admin,artefactual/archivematica-fpr-admin,artefactual/archivematica-fpr-admin