Admin command to change VLOG verbosity during runtime
Admin command to change VLOG verbosity during runtime

Test Plan: mcrouter unit tests, send __mcrouter__verbosity command:
  [pavlo ~] echo "get __mcrouter__.verbosity" | nc 0 5000
  VALUE __mcrouter__.verbosity 0 1
  1
  END
  [pavlo ~] echo "get __mcrouter__.verbosity(5)" | nc 0 5000
  VALUE __mcrouter__.verbosity(5) 0 23
  1 -> 5
  END

Reviewed By: @spalamarchuk

Differential Revision: D1969339
leitao/mcrouter,evertrue/mcrouter,zhlong73/mcrouter,is00hcw/mcrouter,facebook/mcrouter,easyfmxu/mcrouter,facebook/mcrouter,tempbottle/mcrouter,nvaller/mcrouter,reddit/mcrouter,reddit/mcrouter,zhlong73/mcrouter,leitao/mcrouter,nvaller/mcrouter,easyfmxu/mcrouter,apinski-cavium/mcrouter,evertrue/mcrouter,glensc/mcrouter,facebook/mcrouter,reddit/mcrouter,apinski-cavium/mcrouter,yqzhang/mcrouter,synecdoche/mcrouter,reddit/mcrouter,easyfmxu/mcrouter,nvaller/mcrouter,apinski-cavium/mcrouter,evertrue/mcrouter,apinski-cavium/mcrouter,yqzhang/mcrouter,leitao/mcrouter,tempbottle/mcrouter,zhlong73/mcrouter,tempbottle/mcrouter,nvaller/mcrouter,synecdoche/mcrouter,yqzhang/mcrouter,easyfmxu/mcrouter,is00hcw/mcrouter,tempbottle/mcrouter,glensc/mcrouter,facebook/mcrouter,is00hcw/mcrouter,glensc/mcrouter,zhlong73/mcrouter,synecdoche/mcrouter,glensc/mcrouter,evertrue/mcrouter,is00hcw/mcrouter,yqzhang/mcrouter,leitao/mcrouter,synecdoche/mcrouter