Python ignores SIGPIPE on startup, because it prefers to check every
write and raise an IOError exception rather than taking the signal. Most
Unix subprocesses don't expect to work this way. This patch (adapted
from Colin Watson's post at http://tinyurl.com/2a7mzh5) sets SIGPIPE
back to the default action for nova.utils.execute and nova-rootwrap
created subprocesses.
Fixes bug 1053364
Change-Id: I17e1629bb4ef4268515c6734ddb6e12746739c52
236aecd3e1