common: Improve _link_output_file to be more versatile

common: Improve _link_output_file to be more versatile

Currently _link_output_file() selects output file suffix based on the
current operating system. Make it more versatile by allowing selection
of output file suffix based on any feature string. The idea is that
in config file ($seq.cfg) there are several lines like:

feat1,feat2: suffix

The function is passed a feature string (or uses os_name,MOUNT_OPTIONS
if no argument is passed) and selects output file with a suffix for
which all features are present in the feature string. If there is no
matching line, output with 'default' suffix is selected.

Update all tests using _link_out_file to the new calling convention.

Signed-off-by: Jan Kara <jack@suse.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>