Exit dumpstate on SIGPIPE to avoid cascading child crashes

When dumpstate ignores SIGPIPE it can lead to a cascade of tombstones /
coredumps since many of its children don't handle or ignore it.  It's
best to just exit dumpstate once the pipe is broken.

Change-Id: Ic0c57ecf4171f0c0a07837e51c41cb1876e1350c