slapos-sr-testing: Add caucase

Caucase binaries are required for some testing scenarios.

software/slapos-sr-testing/software.cfg

@@ -236,6 +236,7 @@ extra-eggs =
   ${slapos.core-setup:egg}
   ${pillow-python:egg}
   ${pycurl:egg}
+  caucase
   erp5.util
   ${python-pynacl:egg}
   ${python-cryptography:egg}