test/dashboard: fix segfault when importing dm.xmlsec.binding

python-saml depends on dm.xmlsec.binding which is a python binding of
xmlsec C library. but without -DXMLSEC_NO_SIZE_T the compiled
dm.xmlsec.binding segfaults when `import dm.xmlsec.binding`. see
SAML-Toolkits/python-saml#30 and
4teamwork/ftw.saml2auth#3 .

in long term, we might want to switch to python-saml, see
http://tracker.ceph.com/issues/37081

Signed-off-by: Kefu Chai <kchai@redhat.com>

src/pybind/mgr/dashboard/tox.ini

@@ -10,6 +10,7 @@ deps =
     py27: -r{toxinidir}/requirements-py27.txt
     py3: -r{toxinidir}/requirements-py3.txt
 setenv=
+    CFLAGS = -DXMLSEC_NO_SIZE_T
     UNITTEST = true
     WEBTEST_INTERACTIVE = false
     LD_LIBRARY_PATH = {toxinidir}/../../../../build/lib