Squashed commit of the following:

Squashed commit of the following:

commit 950f04df117bf246cfa9a2fa99bf12a64d6bd0a4
Author: Costa Tsaousis (ktsaou) <costa@tsaousis.gr>
Date:   Sun Apr 3 23:47:06 2016 +0300

    dont keep the pidfd open

commit bd45505d0177703940b2393a5e36b3e80b912ff1
Author: Costa Tsaousis (ktsaou) <costa@tsaousis.gr>
Date:   Sun Apr 3 23:33:18 2016 +0300

    dont unlink pidfile at start

commit 4afd30e81d3cd70400162c7603b659fd35160c8b
Author: Costa Tsaousis (ktsaou) <costa@tsaousis.gr>
Date:   Sun Apr 3 23:30:47 2016 +0300

    close pidfile then unlink

commit faf66f4f5f39bda8d0b5e947afbdb8cd1ac505be
Author: Costa Tsaousis (ktsaou) <costa@tsaousis.gr>
Date:   Sun Apr 3 19:38:49 2016 +0300

    fix to keep close the file if it has been successfully chwoned

commit 0af1e73e6db3b681e8303ee394fc2ac003db6e67
Author: Costa Tsaousis (ktsaou) <costa@tsaousis.gr>
Date:   Sun Apr 3 19:35:31 2016 +0300

    chown pidfile only when dropping privileges; do not keep the pidfile open when not dropping privileges

commit 550c9f8e9757f5a5767d11764a80f7736c197b37
Author: Costa Tsaousis (ktsaou) <costa@tsaousis.gr>
Date:   Sun Apr 3 19:15:32 2016 +0300

    do not chown pidfile

commit ca808d2231ed175397408ea436a50642e10cd281
Author: Costa Tsaousis (ktsaou) <costa@tsaousis.gr>
Date:   Sun Apr 3 18:57:30 2016 +0300

    added command line parameter -pidfile; the pidfile is only generated if this parameter is passed; #151 #156