`rerun_filter` called twice per test

I am finding that the `rerun_filter` function is called twice per test.

Version: 3.6.1
Pytest version: 5.4.3

Here is some sample code to recreate the problem:
```
def my_rerun_filter(*args):
log.debug("ran filter")
return True

runs = 0
class TestFlaky:

@flaky(max_runs=10, rerun_filter=my_rerun_filter)
def test_4_fails(self):
global runs
runs += 1
log.debug("ran test {}".format(runs))
if runs < 5:
raise ValueError()
```

This logs `ran filter` 8 times even though the test only runs 4 times. A stack trace shows that the `flaky_pytest_plugin.py` will call `self._should_rerun_test` twice: once at line 92 and once at line 101.

Relevant stack traces:
```
File "/Users/rwoo/rwoo/lib/python3.6/site-packages/flaky/flaky_pytest_plugin.py", line 92, in pytest_runtest_protocol
self.runner.pytest_runtest_protocol(item, nextitem)
File "/Users/rwoo/rwoo/lib/python3.6/site-packages/_pytest/runner.py", line 85, in pytest_runtest_protocol
runtestprotocol(item, nextitem=nextitem)
File "/Users/rwoo/rwoo/lib/python3.6/site-packages/_pytest/runner.py", line 100, in runtestprotocol
reports.append(call_and_report(item, "call", log))
File "/Users/rwoo/rwoo/lib/python3.6/site-packages/flaky/flaky_pytest_plugin.py", line 141, in call_and_report
if self._will_handle_test_error_or_failure(item, name, err):
File "/Users/rwoo/rwoo/lib/python3.6/site-packages/flaky/_flaky_plugin.py", line 152, in _will_handle_test_error_or_failure
return self._should_handle_test_error_or_failure(test) and self._should_rerun_test(test, name, err)

File "/Users/rwoo/rwoo/lib/python3.6/site-packages/flaky/flaky_pytest_plugin.py", line 101, in pytest_runtest_protocol
should_rerun = not skipped and self.add_failure(item, call_info.excinfo)
File "/Users/rwoo/rwoo/lib/python3.6/site-packages/flaky/flaky_pytest_plugin.py", line 327, in add_failure
return self._handle_test_error_or_failure(item, error)
File "/Users/rwoo/rwoo/lib/python3.6/site-packages/flaky/_flaky_plugin.py", line 190, in _handle_test_error_or_failure
if self._should_rerun_test(test, name, err):
```