Avoided sending `LostSlaveMessage` to disconnected frameworks.
Avoided sending `LostSlaveMessage` to disconnected frameworks.

Since we don't attempt to send messages to disconnected frameworks, this
would only have resulted in a warning message in the master logs anyway.

Review: https://reviews.apache.org/r/53893/

kaysoky/mesos,kaysoky/mesos,andschwa/mesos,chhsia0/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,Gilbert88/mesos,verizonlabs/mesos,zmalik/mesos,neilconway/mesos,neilconway/mesos,jpeach/mesos,craimbert/mesos,dforsyth/mesos,gsantovena/mesos,abudnik/mesos,dforsyth/mesos,neilconway/mesos,asamerh4/mesos,zmalik/mesos,abudnik/mesos,Gilbert88/mesos,Gilbert88/mesos,dforsyth/mesos,chhsia0/mesos,dforsyth/mesos,andschwa/mesos,verizonlabs/mesos,reneploetz/mesos,craimbert/mesos,zmalik/mesos,asamerh4/mesos,chhsia0/mesos,verizonlabs/mesos,chhsia0/mesos,neilconway/mesos,asamerh4/mesos,gsantovena/mesos,abudnik/mesos,zmalik/mesos,jpeach/mesos,yuquanshan/customizedMesos,abudnik/mesos,asamerh4/mesos,kaysoky/mesos,asamerh4/mesos,jpeach/mesos,jpeach/mesos,yuquanshan/customizedMesos,craimbert/mesos,zmalik/mesos,reneploetz/mesos,neilconway/mesos,gsantovena/mesos,dforsyth/mesos,yuquanshan/customizedMesos,andschwa/mesos,kaysoky/mesos,Gilbert88/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,abudnik/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,andschwa/mesos,Aman-Jain-14/customizedMesos,reneploetz/mesos,dforsyth/mesos,kaysoky/mesos,craimbert/mesos,jpeach/mesos,Aman-Jain-14/customizedMesos,reneploetz/mesos,abudnik/mesos,asamerh4/mesos,yuquanshan/customizedMesos,craimbert/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,Gilbert88/mesos,neilconway/mesos,Aman-Jain-14/customizedMesos,dforsyth/mesos,verizonlabs/mesos,verizonlabs/mesos,asamerh4/mesos,Gilbert88/mesos,abudnik/mesos,gsantovena/mesos,jpeach/mesos,gsantovena/mesos,yuquanshan/customizedMesos,kaysoky/mesos,yuquanshan/customizedMesos,chhsia0/mesos,gsantovena/mesos,andschwa/mesos,reneploetz/mesos,craimbert/mesos,zmalik/mesos,chhsia0/mesos,andschwa/mesos,neilconway/mesos,zmalik/mesos,andschwa/mesos,verizonlabs/mesos,reneploetz/mesos,jpeach/mesos,craimbert/mesos,kaysoky/mesos,reneploetz/mesos,Gilbert88/mesos