vnctl does not accept RFC-compliant UUIDs

[miz-axsh]

UUIDs compliant with RFC 4122 are rejected.
Passing UUIDs generated by uuidgen(1) causes an error:

# vnctl datapaths add \
         --uuid=f5a6ca6f-7032-4dbd-9245-1e799ff48c14 \
         --display-name=detapath01 \
         --dpid=0x0000deadbeefcafe \
         --node-id=vna
---
:error: Vnet::Endpoints::Errors::InvalidUUID
:message: 'Datapath#uuid: f5a6ca6f-7032-4dbd-9245-1e799ff48c14'
:code: '101'

this seems to be limited by regex {prefix}-[a-z0-9]{1,16}.

RFC-compliant UUIDs are widely used, and also supported by mysql: SELECT UUID();.
https://en.wikipedia.org/wiki/Universally_unique_identifier
https://tools.ietf.org/html/rfc4122