Reporting: Make HTML reports for bisection flights too

Reporting: Make HTML reports for bisection flights too

Provide an appropriate --html-dir option to sg-report-flight.
(Bisection flights still do not run sg-report-host-history and
sg-report-job-history, which are fairly expensive.)

Make references to jobs from sg-report-job-history and
sg-report-host-history go to the /info.html page, not the webserver
directory listing.  (sg-report-flight's references already do.)

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>