hydra: if a project or jobset is hidden (and thus disabled) do not keep builds

Dependencies

• [2] NEWDDAOF * Allow users to change the value of a build's "keep" flag, which
• [3] 4X6NS66Q * Keep the most recent builds for each job.
• [4] WZ3AEJ67 * hydra_update_gc_roots.pl registers build outputs that should be kept
• [5] IN272KZW * Automatically keep all builds in the latest successful release in

Change contents

• replacement in src/script/hydra_update_gc_roots.pl at line 37
  [3.1149]→[3.520:576](∅→∅)
  − foreach my $project ($db->resultset('Projects')->all) {
  [3.1149]

  [3.3700]
  + foreach my $project ($db->resultset('Projects')->search({hidden => 0},{})) {
• replacement in src/script/hydra_update_gc_roots.pl at line 41
  [3.577]→[2.1659:1703](∅→∅)
  − foreach my $job ($project->jobs->all) {
  [3.577]

  [2.1703]
  + foreach my $job ($project->jobs->search({hidden => 0}, { join => "jobset"})) {