Update tests after miss-on-get removal

[mszabo-wikia]

Since D73554883, mcrouter no longer converts GET errors to misses, which necessitates updating some relevant tests:

• Update test_mcrouter_serialized and test_mcrouter_states to expect an error response instead of a miss where necessary.
• Update CarbonRouterClient.basicUsageRemoteThreadClientThreadAffinityMulti to also accept a CONNECT_TIMEOUT as an expected error response (this may be the case on some local systems and GitHub Actions). Make the assertion less cryptic.

Original errors from CI:

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FAIL: test_failover_limit (mcrouter.test.test_mcrouter_serialized.TestFailoverWithLimit)
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Traceback (most recent call last):
  File "/tmp/fbcode_builder_getdeps-ZhomeZrunnerZworkZmcrouterZmcrouterZbuildZfbcode_builder/build/mcrouter-CeBnYGY6hczXARtSui5EWvho5spSAKd88uS5EUCPCYM/mcrouter/test/test_mcrouter_serialized.py", line 260, in test_failover_limit
    self.assertIsNone(mcr.get("key"))
AssertionError: 'SERVER_ERROR 307 busy' is not None

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FAIL: test_failover_limit (mcrouter.test.test_mcrouter_serialized.TestFailoverWithLimitWithErrors)
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Traceback (most recent call last):
  File "/tmp/fbcode_builder_getdeps-ZhomeZrunnerZworkZmcrouterZmcrouterZbuildZfbcode_builder/build/mcrouter-CeBnYGY6hczXARtSui5EWvho5spSAKd88uS5EUCPCYM/mcrouter/test/test_mcrouter_serialized.py", line 317, in test_failover_limit
    self.assertIsNone(mcr.get("key"))
AssertionError: 'SERVER_ERROR Reply timeout' is not None

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FAIL: test_failover_limit (mcrouter.test.test_mcrouter_serialized.TestFailoverWithLimitWithTKO)
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Traceback (most recent call last):
  File "/tmp/fbcode_builder_getdeps-ZhomeZrunnerZworkZmcrouterZmcrouterZbuildZfbcode_builder/build/mcrouter-CeBnYGY6hczXARtSui5EWvho5spSAKd88uS5EUCPCYM/mcrouter/test/test_mcrouter_serialized.py", line 287, in test_failover_limit
    self.assertIsNone(mcr.get("key"))
AssertionError: 'SERVER_ERROR 307 busy' is not None

======================================================================
FAIL: test_failover_limit (mcrouter.test.test_mcrouter_serialized.TestFailoverWithLimitWithTKOAndErrors)
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Traceback (most recent call last):
  File "/tmp/fbcode_builder_getdeps-ZhomeZrunnerZworkZmcrouterZmcrouterZbuildZfbcode_builder/build/mcrouter-CeBnYGY6hczXARtSui5EWvho5spSAKd88uS5EUCPCYM/mcrouter/test/test_mcrouter_serialized.py", line 349, in test_failover_limit
    self.assertIsNone(mcr.get("key"))
AssertionError: 'SERVER_ERROR 307 busy' is not None

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Ran 10 tests in 37.751s

FAILED (failures=4)

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FAIL: test_mcrouter_states (mcrouter.test.test_mcrouter_states.TestMcrouterStates)
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Traceback (most recent call last):
  File "/tmp/fbcode_builder_getdeps-ZhomeZrunnerZworkZmcrouterZmcrouterZbuildZfbcode_builder/build/mcrouter-CeBnYGY6hczXARtSui5EWvho5spSAKd88uS5EUCPCYM/mcrouter/test/test_mcrouter_states.py", line 64, in test_mcrouter_states
    self.assertEqual(mcr.get("key"), None)
AssertionError: 'SERVER_ERROR Server unavailable. Reason: mc_res_connect_error' != None

 [ RUN      ] CarbonRouterClient.basicUsageRemoteThreadClientThreadAffinityMulti
/home/runner/work/mcrouter/mcrouter/mcrouter/test/cpp_unit_tests/McrouterClientUsage.cpp:303: Failure
Value of: *reply.result_ref() == carbon::Result::CONNECT_ERROR || *reply.result_ref() == carbon::Result::TKO
  Actual: false
Expected: true