+++ This bug was initially created as a clone of Bug #1724622 +++

Description of problem:
This failure was found on an RHOSP platform with TripleO deployed configuration, a gist of which is:

1) Setup a mod-wsgi proxy for the manila-api with Apache
2) Expose the manila endpoints via haproxy
3) Run manila microversion tempest tests

manila_tempest_tests.tests.api.test_microversions.MicroversionsTest.test_microversions_v1_no_version[api,positive] (from manila)

Stacktrace

Traceback (most recent call last):
testtools.testresult.real._StringException: Empty attachments:
  pythonlogging:''

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/manila_tempest_tests/tests/api/test_microversions.py", line 71, in test_microversions_v1_no_version
    self.assertEqual(API_MICROVERSIONS_HEADER, resp.get('vary'))
  File "/usr/lib/python2.7/site-packages/testtools/testcase.py", line 350, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/usr/lib/python2.7/site-packages/testtools/testcase.py", line 435, in assertThat
    raise mismatch_error
testtools.matchers._impl.MismatchError: !=:
reference = 'X-OpenStack-Manila-API-Version'
actual = 'X-OpenStack-Manila-API-Version,Accept-Encoding'