(PDB-1268) Add validation for benchmark parameters
(PDB-1268) Add validation for benchmark parameters

This adds validation that nummsgs or runinterval is used, and adds numhosts to
the list or required parameters.

mullr/puppetdb,ajroetker/puppetdb,waynr/puppetdb,senior/puppetdb,mullr/puppetdb,shrug/puppetdb,kbarber/puppetdb,wkalt/puppetdb,waynr/puppetdb,grimradical/puppetdb,kbarber/puppetdb,mullr/puppetdb,shrug/puppetdb,kbarber/puppetdb,ajroetker/puppetdb,shrug/puppetdb,ajroetker/puppetdb,wkalt/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,kbrezina/puppetdb,puppetlabs/puppetdb,waynr/puppetdb,kbarber/puppetdb,highb/puppetdb,wkalt/puppetdb,highb/puppetdb,senior/puppetdb,senior/puppetdb,rbrw/puppetdb,kbrezina/puppetdb,rbrw/puppetdb,puppetlabs/puppetdb,shrug/puppetdb,grimradical/puppetdb,puppetlabs/puppetdb,highb/puppetdb,wkalt/puppetdb,highb/puppetdb,ajroetker/puppetdb,mullr/puppetdb,senior/puppetdb,grimradical/puppetdb,rbrw/puppetdb,grimradical/puppetdb,mullr/puppetdb,kbrezina/puppetdb,rbrw/puppetdb,puppetlabs/puppetdb,waynr/puppetdb,kbrezina/puppetdb