Changes to setup.py

- Adds cryptography as a dependency before pyopenssl
- Modified pyopenssl to lower case to satisfy pip call

setup.py

@@ -51,10 +51,11 @@ def main():
           download_url='https://github.com/apel/ssm/releases',
           license='Apache License, Version 2.0',
           install_requires=[
+              'cryptography==3.3.0',
               'stomp.py<5.0.0',
               'python-ldap<3.4.0',
               'setuptools',
-              'PyOpenSSL',
+              'pyopenssl<=21.0.0',
           ],
           extras_require={
               'AMS': ['argo-ams-library', 'certifi<2020.4.5.2', ],