Fix staging integration tests against legacy environment

[daka1510]

Summary

Change makes sure to run pulse tests only against pulse backends. Needed for staging where simulators pretend to be real backends but don't have pulse defaults.

Details and comments

Fixes broken integration tests against legacy-staging

FAIL: test_device_properties_and_defaults (test.test_basic_server_paths.TestBasicServerPaths) (hgp='***')
Test device properties and defaults.
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Traceback (most recent call last):
  File "/home/runner/work/qiskit-ibm-runtime/qiskit-ibm-runtime/test/test_basic_server_paths.py", line 55, in test_device_properties_and_defaults
    self.assertIsNotNone(pulse_backends[0].defaults())
AssertionError: unexpectedly None

Verified locally

[rathishcholarajan]

LGTM!