Check parent-less Mdm::Platform for relative_name collision

MSP-8995

db/seeds.rb was only checking if an Mdm::Platform existed if parent was
not nil because parent.id needed to be passed, but instead, when parent
is nil, then :parent_id should be passed as nil.
Bump Version

MSFP 8995

Forgot to increment patch version.
Land limhoff-r7/metasploit_data_models#43

fix seed idempotence