Removed unnecessary '--all-cpus' option from perf documentation.
Removed unnecessary '--all-cpus' option from perf documentation.

This flag is the deafult when no target cpus are specified, so
there is no need to include it.

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