Use python slice on password salt instead of Jinja2 truncate()
Use python slice on password salt instead of Jinja2 truncate()

Installing Ansible 2.3 installs Jinja2 v2.9.6 (up from v2.8.1).
Jinja2 v 2.9.4 changed the truncate.leeway default from 0 to 5 chars,
resulting in no truncation for salts up to 21 characters, potentially causing
`salt too large (sha512_crypt requires <= 16 chars)` failure.
Adding a final parameter `0` (leeway) resolves the issue in Ansible 2.3,
but fails on earlier versions with Jinja2 < 2.9.4, causing the error
`do_truncate() takes at most 4 arguments (5 given)`.
This commit switches to python slice [:16] because it works in all contexts.

cimocimocimo/cimo-wordpress-server,jeffstieler/bedrock-ansible,partounian/trellis,Twansparant/trellis-db-sync,pressbooks/trellis,mAAdhaTTah/bedrock-ansible,buluma/trellis,mAAdhaTTah/bedrock-ansible,buluma/trellis,kalenjohnson/trellis,kalenjohnson/trellis,NicBeltramelli/trellis,proteusthemes/pt-ops,roots/bedrock-ansible,pressbooks/trellis,partounian/trellis,NicBeltramelli/trellis,fullyint/trellis,roots/trellis,proteusthemes/pt-ops,partounian/trellis,Twansparant/trellis-db-sync,proteusthemes/pt-ops,partounian/trellis,roots/trellis,NicBeltramelli/trellis,roots/bedrock-ansible,cimocimocimo/cimo-wordpress-server,newtonne/trellis,fullyint/trellis,jeffstieler/bedrock-ansible,newtonne/trellis,cimocimocimo/cimo-wordpress-server,newtonne/trellis,kalenjohnson/trellis,mAAdhaTTah/bedrock-ansible,kalenjohnson/trellis,buluma/trellis,Twansparant/trellis-db-sync,jeffstieler/bedrock-ansible,NicBeltramelli/trellis,fullyint/trellis,cimocimocimo/cimo-wordpress-server,buluma/trellis,mAAdhaTTah/bedrock-ansible,fullyint/trellis,Twansparant/trellis-db-sync