This commit disables new cgo pprof tests and adds an handler in sigtramp
to refuse SIGPROF signal.

Updates #28555

Change-Id: I152a871f8636e93328d411329104c6f023bd1691
Reviewed-on: https://go-review.googlesource.com/c/go/+/164013
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>