Allow redirecting port_server's stdout to separate log file.
Allow redirecting port_server's stdout to separate log file.

Change-Id: I44050404f80fbd9380e6cbe1856f9f4bd2515401
Reviewed-on: http://review.couchbase.org/44859
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,mschoch/ns_server,nimishzynga/ns_server,mschoch/ns_server,mschoch/ns_server,nimishzynga/ns_server,ceejatec/ns_server,ceejatec/ns_server,nimishzynga/ns_server,membase/ns_server,mschoch/ns_server,ceejatec/ns_server,nimishzynga/ns_server,membase/ns_server,membase/ns_server,nimishzynga/ns_server,mschoch/ns_server,ceejatec/ns_server