Merge pull request #174 from mattkirby/pooler_48

(POOLER-48) Clear migrations at application start time

lib/vmpooler/pool_manager.rb

@@ -719,6 +719,8 @@ module Vmpooler
 
       # Clear out the tasks manager, as we don't know about any tasks at this point
       $redis.set('vmpooler__tasks__clone', 0)
+      # Clear out vmpooler__migrations since stale entries may be left after a restart
+      $redis.del('vmpooler__migration')
 
       loop do
         if ! $threads['disk_manager']