Description of problem:
allowed_network_downtime is configured as an integer option while
a default value is set to a float number. When a user tries to
override the option with another float number he receives a ValueError.
This patch changes the option to allow overriding with a float
number.

Version-Release number of selected component (if applicable):
RHOS-17.1-RHEL-9-20221215.n.1

How reproducible:
100% when a user tries to override allowed_network_downtime with a float number (since a default float value of 5.0 confuses the user). Overriding with an integer value works.

Steps to Reproduce:
1.Put into tempest.conf under [validation] section a value  allowed_network_downtime = 6.0
2.Try to run a test, e.g. 'stestr run tempest.scenario.test_network_advanced_server_ops.TestNetworkAdvancedServerOps.test_server_connectivity_live_migration' or just    'stestr list'


Actual results:
Failed to import test module: tempest.api.compute.admin.test_create_server
Traceback (most recent call last):
  File "/usr/lib/python3.9/site-packages/oslo_config/cfg.py", line 2720, in _do_get
    return (convert(val), alt_loc)
  File "/usr/lib/python3.9/site-packages/oslo_config/cfg.py", line 2689, in convert
    return self._convert_value(
  File "/usr/lib/python3.9/site-packages/oslo_config/cfg.py", line 2817, in _convert_value
    return opt.type(value)
  File "/usr/lib/python3.9/site-packages/oslo_config/types.py", line 311, in __call__
    value = self.num_type(value)
ValueError: invalid literal for int() with base 10: '6.0'


Expected results:
No errors


Additional info: