[RFR] Implement test for customer BZ 1703278 (backup to /tmp)

[jarovo]

Purpose or Intent

PRT Run

The BZ is fixed in the first 5.11 we have. The last unfixed CFME is 5.10.5.1. When the filling code is disabled, this command succeeds:

py.test --use-sprout --sprout-group downstream-510z -sv --use-provider complete 'cfme/tests/configure/test_db_backup_schedule.py' --sprout-user-key jhenner --pdb  --sprout-version 5.10.5.1 

when enabled, the same cmdline fails with

"[----] E, [2020-09-08T14:40:17.729568 #14300:a40f60] ERROR -- : MIQ(MiqQueue#deliver) Message id: [164], Error: [undefined method `path' for nil:NilClass]"
...
E               cfme.utils.log_validator.FailPatternMatchError: "Pattern 'ERROR': Expected failure pattern found in log."

On newer CFME the test passes even with the /tmp almost full (all the code in this PR enablde). This makes me sure the test is working fine and it will fail on regression.

[dajoRH]

I detected some fixture changes in commit c66e488

The local fixture appliance_with_tmp_filled is used in the following files:

• cfme/tests/configure/test_db_backup_schedule.py
  • test_db_backup_schedule

Please, consider creating a PRT run to make sure your fixture changes do not break existing usage 😃