qa/suites/rados/mgr: ignorelist MGR_INFLUX_DB_LIST_FAILED in module_selftest

qa/suites/rados/mgr: ignorelist MGR_INFLUX_DB_LIST_FAILED in module_selftest

module_selftest fails on a cluster log warning that is not ignorelisted:

  cluster [WRN] Health check failed: Failed to list/create InfluxDB database (MGR_INFLUX_DB_LIST_FAILED)

module_selftest is the only job that enables the influx module, and no suite
provisions an InfluxDB server, so once enabled the module cannot reach a backend
and raises a health warning: MGR_INFLUX_NO_SERVER when no hostname is set,
MGR_INFLUX_DB_LIST_FAILED from serve() once one is.  test_influx sets a hostname,
so it hits the latter.

This surfaced only after the test image started shipping the influxdb python
module.  Until then can_run() returned false, the module never enabled, and the
sole log line was "influxdb python module not found", which is already
ignorelisted.  self_test() cannot run without enabling the module, so ignorelist
the warning it raises.

Signed-off-by: Kefu Chai <k.chai@proxmox.com>