(packaging) Bump version to 5.1.1-SNAPSHOT
(packaging) Bump version to 5.1.1-SNAPSHOT

This commit updates puppetserver's version to the next snapshot version
following the 5.1.0 release.

puppetlabs/puppet-server,puppetlabs/puppetserver,puppetlabs/puppetserver,puppetlabs/puppet-server,puppetlabs/puppetserver,puppetlabs/puppet-server,puppetlabs/puppetserver