Optimized resources logging in master.
Optimized resources logging in master.

When master logs agent or task resources, it uses `operator <<` for raw
protobuf data, which outputs resources in JSON format, and is rather
slow. However resources are known to be valid and refined when logged by
master, so it's faster to use `operator <<` after protobuf is converted
to `Resources`.

Review: https://reviews.apache.org/r/63959/

andschwa/mesos,reneploetz/mesos,gsantovena/mesos,abudnik/mesos,reneploetz/mesos,reneploetz/mesos,dforsyth/mesos,chhsia0/mesos,gsantovena/mesos,asamerh4/mesos,andschwa/mesos,abudnik/mesos,chhsia0/mesos,kaysoky/mesos,Gilbert88/mesos,kaysoky/mesos,chhsia0/mesos,kaysoky/mesos,chhsia0/mesos,Gilbert88/mesos,chhsia0/mesos,jpeach/mesos,abudnik/mesos,dforsyth/mesos,jpeach/mesos,Gilbert88/mesos,chhsia0/mesos,Gilbert88/mesos,andschwa/mesos,dforsyth/mesos,asamerh4/mesos,Gilbert88/mesos,gsantovena/mesos,gsantovena/mesos,jpeach/mesos,gsantovena/mesos,asamerh4/mesos,Gilbert88/mesos,reneploetz/mesos,abudnik/mesos,andschwa/mesos,asamerh4/mesos,reneploetz/mesos,reneploetz/mesos,jpeach/mesos,gsantovena/mesos,jpeach/mesos,Gilbert88/mesos,reneploetz/mesos,dforsyth/mesos,jpeach/mesos,asamerh4/mesos,abudnik/mesos,chhsia0/mesos,dforsyth/mesos,kaysoky/mesos,abudnik/mesos,abudnik/mesos,dforsyth/mesos,jpeach/mesos,dforsyth/mesos,andschwa/mesos,andschwa/mesos,kaysoky/mesos,asamerh4/mesos,andschwa/mesos,kaysoky/mesos,asamerh4/mesos,kaysoky/mesos,gsantovena/mesos