(maint) Bump to ezbake 1.7.3
(maint) Bump to ezbake 1.7.3

This commit updates to the latest version of ezbake, which will set build_tar
to false, preventing the nightlies job from attempting to sign tars that don't
exist.

puppetlabs/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,puppetlabs/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,rbrw/puppetdb,rbrw/puppetdb,rbrw/puppetdb,puppetlabs/puppetdb