Code Review: Fix to-disk queue infinite growth.
Code Review: Fix to-disk queue infinite growth.

We discovered a bug while manually testing this branch on a live
instance, whereby the to-disk queue was never actually dumped to
disk.

alileza/prometheus,Colstuwjx/prometheus,brancz/prometheus,GoogleCloudPlatform/prometheus,Stackdriver/stackdriver-prometheus,rajthilakmca/prometheus,wrouesnel/prometheus,laushinka/prometheus,flier/prometheus,PrFalken/prometheus,gottwald/prometheus,Dieterbe/prometheus,GoogleCloudPlatform/prometheus,yanghongkjxy/prometheus,gottwald/prometheus,RobertKielty/prometheus,trigrass2/prometheus,q3k/prometheus,jbdalido/prometheus,nicr9/prometheus,slok/prometheus,bluecmd/prometheus,wxdublin/prometheus,cit-lab/prometheus,laushinka/prometheus,sudhi-vm/prometheus,jmcfarlane/prometheus,yanghongkjxy/prometheus,Stackdriver/stackdriver-prometheus,amorken/prometheus,Gouthamve/prometheus,thachmai/prometheus,abhishekamralkar/prometheus,hustbill/prometheus,JavierZunzunegui/prometheus,ton31337/prometheus,iksaif/prometheus,GoogleCloudPlatform/prometheus,brancz/prometheus,SaltedMan/prometheus-annotated,kangwoo/prometheus,jbdalido/prometheus,mrwacky42/prometheus,brancz/prometheus,JavierZunzunegui/prometheus,fabxc/prometheus,tomwilkie/prometheus,gottwald/prometheus,prometheus/prometheus,fabric8io/prometheus,ton31337/prometheus,jmcfarlane/prometheus,alileza/prometheus,sudhi-vm/prometheus,brian-brazil/prometheus,bluecmd/prometheus,adamron1/prometheus,PrFalken/prometheus,sudhi-vm/prometheus,cit-lab/prometheus,dln/prometheus,flier/prometheus,rajthilakmca/prometheus,Gouthamve/prometheus,dpatel06/prometheus,slok/prometheus,mrwacky42/prometheus,nicr9/prometheus,kzittritsch/prometheus,fabxc/prometheus,dalanlan/prometheus,kzittritsch/prometheus,dpatel06/prometheus,abhishekamralkar/prometheus,trigrass2/prometheus,jimmidyson/prometheus,adamron1/prometheus,dalanlan/prometheus,prometheus/prometheus,kangwoo/prometheus,jbdalido/prometheus,slok/prometheus,tomwilkie/prometheus,wndhydrnt/prometheus,jbdalido/prometheus,jmcfarlane/prometheus,iksaif/prometheus,laushinka/prometheus,cit-lab/prometheus,keegancsmith/prometheus,JavierZunzunegui/prometheus,PrFalken/prometheus,sudhi-vm/prometheus,thachmai/prometheus,justintung/prometheus,Dieterbe/prometheus,q3k/prometheus,gcnonato/prometheus,prasincs/prometheus,hustbill/prometheus,keegancsmith/prometheus,hustbill/prometheus,datajet-io/prometheus,gcnonato/prometheus,RobertKielty/prometheus,AlekSi/prometheus,amorken/prometheus,msiebuhr/prometheus,Gouthamve/prometheus,tattsun/prometheus,tattsun/prometheus,msiebuhr/prometheus,yanghongkjxy/prometheus,prometheus/prometheus,nicr9/prometheus,brian-brazil/prometheus,dln/prometheus,Colstuwjx/prometheus,abhishekamralkar/prometheus,msiebuhr/prometheus,eliothedeman/prometheus,agaoglu/prometheus,AlekSi/prometheus,robbiet480/prometheus,datajet-io/prometheus,tomwilkie/prometheus,dmilstein/prometheus,GoogleCloudPlatform/prometheus,smyrman/prometheus,AlekSi/prometheus,brian-brazil/prometheus,slok/prometheus,Colstuwjx/prometheus,msiebuhr/prometheus,datajet-io/prometheus,wndhydrnt/prometheus,datajet-io/prometheus,Colstuwjx/prometheus,q3k/prometheus,dmilstein/prometheus,wrouesnel/prometheus,keegancsmith/prometheus,Conorbro/prometheus,fabric8io/prometheus,AlekSi/prometheus,gcnonato/prometheus,amorken/prometheus,jimmidyson/prometheus,alileza/prometheus,dsymonds/prometheus,wrouesnel/prometheus,agaoglu/prometheus,mrwacky42/prometheus,adamron1/prometheus,prasincs/prometheus,ton31337/prometheus,iksaif/prometheus,tattsun/prometheus,dmilstein/prometheus,justintung/prometheus,dpatel06/prometheus,PrFalken/prometheus,laushinka/prometheus,bluecmd/prometheus,smyrman/prometheus,adamron1/prometheus,gesellix/prometheus,prasincs/prometheus,thachmai/prometheus,dsymonds/prometheus,mtanda/prometheus,jmcfarlane/prometheus,prometheus/prometheus,dln/prometheus,Conorbro/prometheus,trigrass2/prometheus,gottwald/prometheus,eliothedeman/prometheus,alileza/prometheus,fabric8io/prometheus,kangwoo/prometheus,robbiet480/prometheus,trigrass2/prometheus,fabxc/prometheus,hustbill/prometheus,Stackdriver/stackdriver-prometheus,keegancsmith/prometheus,mtanda/prometheus,eliothedeman/prometheus,SaltedMan/prometheus-annotated,Conorbro/prometheus,dsymonds/prometheus,Gouthamve/prometheus,Stackdriver/stackdriver-prometheus,flier/prometheus,abhishekamralkar/prometheus,smyrman/prometheus,dsymonds/prometheus,justintung/prometheus,prometheus/prometheus,wxdublin/prometheus,wndhydrnt/prometheus,bluecmd/prometheus,gcnonato/prometheus,rajthilakmca/prometheus,rajthilakmca/prometheus,cit-lab/prometheus,eliothedeman/prometheus,prasincs/prometheus,dln/prometheus,wxdublin/prometheus,kzittritsch/prometheus,smyrman/prometheus,fabxc/prometheus,keegancsmith/prometheus,agaoglu/prometheus,dmilstein/prometheus,justintung/prometheus,iksaif/prometheus,JavierZunzunegui/prometheus,RobertKielty/prometheus,kzittritsch/prometheus,wrouesnel/prometheus,Dieterbe/prometheus,amorken/prometheus,gesellix/prometheus,thachmai/prometheus,gesellix/prometheus,SaltedMan/prometheus-annotated,ton31337/prometheus,mtanda/prometheus,fabric8io/prometheus,agaoglu/prometheus,mtanda/prometheus,robbiet480/prometheus,tomwilkie/prometheus,gesellix/prometheus,brancz/prometheus,jimmidyson/prometheus,dalanlan/prometheus,robbiet480/prometheus,q3k/prometheus,GoogleCloudPlatform/prometheus,SaltedMan/prometheus-annotated,alileza/prometheus,yanghongkjxy/prometheus,Conorbro/prometheus,kangwoo/prometheus,RobertKielty/prometheus,tattsun/prometheus