Impact of the new feature
WMAgent

Is your feature request related to a problem? Please describe.
Yes, this method has been deprecated in HTCondor 10.7.0:

/usr/lib64/python3.9/site-packages/htcondor/_deprecation.py:41: FutureWarning: Schedd.xquery() was deprecated in version 10.7.0 and will be removed in a future release.
  warnings.warn(message, FutureWarning)

so we better migrate (back?) to Schedd.query(), before we have to patch things out.

Describe the solution you'd like
There are a few places in WMAgent codebase that we rely on the Schedd.xquery() method. We need to adopt Schedd.query(), which is supposed to be exactly the same as the former, but instead of returning a generator, it will expand everything in memory.

Describe alternatives you've considered
We are already in a dangerous situation, given that we are now running HTCondor python bindings 10.9.0. So it has to be done.

Additional context
Documentation: https://htcondor.readthedocs.io/en/latest/apis/python-bindings/api/htcondor.html#interacting-with-schedulers
IF needed, please talk to the CRAB folks, has they have already performed this migration.