param: Amend docs.py test to check dumping of flagged parameters

param: Amend docs.py test to check dumping of flagged parameters

This test uses an empty smb.conf file to check if the resulting
output from testparm is empty.

It also sets a parameter as default in an smb.conf file and then
sets the option on the command line to ensure they are displayed
correctly.

Change-Id: I48f05b6e3c9e5cd856e89b196e00ae35eb93bf9f
Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Tue Jul  8 01:57:59 CEST 2014 on sn-devel-104