Use validate_legacy

Use validate_legacy

This changes all the puppet 3 validate_* functions
to use the validate_legacy function.

The validate_legacy function has been available since
about three years but require Puppet >= 4.4.0 and since
there is Puppet 4.10.12 as latest we should assume people
are running a fairly new Puppet 4 version.

This is the first step to then remove all validate function
calls and use proper types for parameter as described in spec [1].

[1] https://review.openstack.org/#/c/568929/

Change-Id: I640d5ca592774601a252dbafbdc90bc98313055b