Fix bad task host selection

It looks like #873 has broken the test battery where the tests concern
bad task hosts.
Merge pull request #875 from matthewrmshin/fix-bad-task-host

Fix bad task host selection
Improve test stability

Add `skip_all` function to skip all tests in a file.
Increase timeout for a suite.
Improve remote passphrase sync logic.
Fix gcylc task insertion (stop cycle was ignored).
Discard tasks that have passed their own stop cycle.

They were being adding to task pool but in the 'held' state, which
could hold up the suite by means of the runahead limit.
Added a test for the insert command (with and without a stop cycle).
Merge pull request #878 from hjoliver/fix-gcylc-task-insertion

Fix gcylc task insertion (stop cycle was ignored).
Merge pull request #879 from hjoliver/discard-tasks-beyond-their-stop-cycle

Discard tasks that have passed their own stop cycle.
Merge pull request #877 from matthewrmshin/improve-test-stability

Improve test stability
Ignore late polling results.
Restore support for user-defined job submission methods.
Merge pull request #881 from hjoliver/restore-user-job-submission-methods

Restore support for user-defined job submission methods.
Added a test to check that we ignore late poll results.
Merge pull request #880 from hjoliver/872.ignore-late-poll-results

Ignore late polling results.
Fix polling on restart for running tasks.
Merge pull request #882 from arjclark/fix.poll_running_on_restart

Fix polling on restart for running tasks.
Support loadleveler job pre-empt/vacation

Handle `SIGUSR1` for loadleveler jobs with `restart=yes` directive.
On receiving a `SIGUSR1` signal, a job script will remove its status
file, and send a message to the suite to indicate that it has been
vacated. The server will reset the status of the task (job) to
`submitted`. This change resolve cylc/cylc#867.
Merge pull request #868 from matthewrmshin/handle-job-vacated-by-sigusr1

Support loadleveler job vacation: handle SIGUSR1
broadcast: allow overlapping inheritance

This allows broadcasts on families to be used with broadcasts on a task.
tests: remove unnecessary line in suite