(maint) Cleanup anonymizer code syntax
(maint) Cleanup anonymizer code syntax

This commit cleans up the code in the anonymizer.clj namespace, notable
changes include moving from using update-in-nil to our utils function
with the same functionality, removing unused variables in a let binding,
refactoring complicated nested conditionals to conds, and changes
`schema/maybe [...]` to `[...]` since schema handles the nil case for
vectors already.

rbrw/puppetdb,rbrw/puppetdb,rbrw/puppetdb,wkalt/puppetdb,kbarber/puppetdb,puppetlabs/puppetdb,waynr/puppetdb,waynr/puppetdb,waynr/puppetdb,puppetlabs/puppetdb,grimradical/puppetdb,puppetlabs/puppetdb,mullr/puppetdb,senior/puppetdb,rbrw/puppetdb,kbarber/puppetdb,kbarber/puppetdb,mullr/puppetdb,puppetlabs/puppetdb,kbarber/puppetdb,grimradical/puppetdb,senior/puppetdb,mullr/puppetdb,wkalt/puppetdb,mullr/puppetdb,puppetlabs/puppetdb,waynr/puppetdb,grimradical/puppetdb,senior/puppetdb,wkalt/puppetdb,mullr/puppetdb,rbrw/puppetdb,grimradical/puppetdb,wkalt/puppetdb,senior/puppetdb