dmesg: don't report EPIPE

Signed-off-by: Karel Zak <kzak@redhat.com>
include/closestream: don't wipe errno on EPIPE

... the code in close_stdout() is sensitive to EPIPE, so
wipe errno is close_stream() is probably bad idea.

Signed-off-by: Karel Zak <kzak@redhat.com>