Make sure we 'sudo kill' our sudo pexpect process in close().

This should more reliably shut down pexpect subprocesses when
build.py exits before completion.
skip test if RT_GROUP_SCHED is not enabled
measure loss with udp iperf
Merge pull request #388 from cdburkard/patches/intfOptions

measure loss with udp iperf
Merge pull request #387 from cdburkard/patches/iperf_bw

use udp with iperf to measure loss. pings are not reliable
Merge pull request #386 from cdburkard/patches/cpu_test

Skip test_cpu.py if RT_GROUP_SCHED is not enabled
Merge branch 'master' of github.com:mininet/mininet into patches/fix_sshd
promote waitListening to util.py