drain-into-vec! should use async consumer API
drain-into-vec! should use async consumer API

This change gives us parity between our test functions and our real code (which
was already ported to use async consumers). It also runs much faster, and cuts
our overall test execution time by several seconds.

Signed-off-by: Deepak Giridharagopal <d11186354d1ef01ca06ae37d7e23e827da13e85f@puppetlabs.com>

jantman/puppetdb,mullr/puppetdb,rbrw/puppetdb,rbrw/puppetdb,senior/puppetdb,stahnma/puppetdb,senior/puppetdb,haus/puppetdb,cprice404/puppetdb,highb/puppetdb,ajroetker/puppetdb,highb/puppetdb,nfagerlund/puppetdb,github/puppetlabs-puppetdb,stahnma/puppetdb,senior/puppetdb,waynr/puppetdb,melissa/puppetdb,puppetlabs/puppetdb,kbrezina/puppetdb,senior/puppetdb,stahnma/puppetdb,rbrw/puppetdb,grimradical/puppetdb,jantman/puppetdb,puppetlabs/puppetdb,github/puppetlabs-puppetdb,grimradical/puppetdb,wkalt/puppetdb,puppetlabs/puppetdb,shrug/puppetdb,highb/puppetdb,wkalt/puppetdb,cprice404/puppetdb,ajroetker/puppetdb,johnduarte/puppetdb,rbrw/puppetdb,mullr/puppetdb,jantman/puppetdb,kbarber/puppetdb,grimradical/puppetdb,kbrezina/puppetdb,shrug/puppetdb,waynr/puppetdb,ajroetker/puppetdb,kbarber/puppetdb,rbrw/puppetdb,haus/puppetdb,shrug/puppetdb,johnduarte/puppetdb,highb/puppetdb,haus/puppetdb,waynr/puppetdb,melissa/puppetdb,cprice404/puppetdb,kbrezina/puppetdb,mullr/puppetdb,mullr/puppetdb,kbarber/puppetdb,kbrezina/puppetdb,wkalt/puppetdb,nfagerlund/puppetdb,grimradical/puppetdb,waynr/puppetdb,mullr/puppetdb,melissa/puppetdb,johnduarte/puppetdb,puppetlabs/puppetdb,johnduarte/puppetdb,wkalt/puppetdb,shrug/puppetdb,ajroetker/puppetdb,puppetlabs/puppetdb,kbarber/puppetdb,nfagerlund/puppetdb,github/puppetlabs-puppetdb