iperf 3.0.2 (new formula)

Net performance measurement tool.
iperf3: add 3.0.2 bottle.

Closes #24971.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
CLT.installed?: base result on version detection

CLT.installed? previously returned false if the user had outdated dev
tools installed after a 10.9 upgrade, which was confusing to users.