We run some nova tasks once per cell, using a condition to match a
single host in the cell. In other similar tasks, we use run_once, which
will fail all hosts if the task fails. Typically these tasks are
critical, and that is desirable. However, with the approach used in
nova-cell to support multiple cells, if a once-per-cell task fails, then
other hosts will continue to execute, which could lead to unexpected
results.

This change adds any_errors_fatal to the plays or blocks that run these
tasks.

Closes-Bug: #1948694

Change-Id: I2a5871ccd4e8198171ef3239ce95f475f3e4b051