Handling errors in daemonAdapter

This patch adds --syslog arguments to daemonAdapter, this option is
needed in order to catch and log possible failures when vdsm is run via sysv,
which does not capture stderr of the service script (which is used by
default).

This patch also introduces daemonAdapter class to simplify the implementation.

Change-Id: Ib515b01f06331d744b40236af5a1b12a16c37871
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/18810
Reviewed-by: Alon Bar-Lev <alonbl@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>