Few changes to toporeader related stuff.

Hoping to increase QPS, no luck so far. Need profiling.
Adding profiling support to servenv, zkclient2.

And the test now collects pprof info.
Just run:
./zkocc_test.py -v TestZkocc.test_vtgate_qps --skip-teardown
Then run:
go tool pprof $VTROOT/bin/vtgate $VTDATAROOT/tmp/vtgate.pprof
(or with zkclient2 for the client side)
and for instance type 'web' in the prompt.
Adding comment to test.
Merge branch 'master' of github.com:youtube/vitess