netcmd: Small tweak to retrieving pwdProperties

netcmd: Small tweak to retrieving pwdProperties

Currently the 'samba-tool domain passwordsettings' command shares a
'set' and 'show' option, but there is very little common code between
the two. The only variable that's shared is pwd_props, but there's a
separate API we can use to get this. This allows us to split the command
into a super-command in a subsequent patch.

Fixed up erroneous comments while I'm at it.

Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>