run-report: Restore SIGPIPE default handler in subprocess calls

run-report: Restore SIGPIPE default handler in subprocess calls

Python override the SIGPIPE default handler because it prefers to check
every write and raise an IOError exception rather than taking SIGPIPE
[1].

This behavior has the unfortunate side-effect of polluting stdout with
broken pipe messages on shell pipelines invocations (e.g. echo foo |
grep something | etc.) in shell scripts spawned via subprocess.Popen().

This commit fix the polluting of stdout by restoring the default SIGPIPE
handler on subprocess calls.

[1] - http://bugs.python.org/issue1652

Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>