Add the ability to use TLS to the redis-session extension

[atgitwk]

Hello,
PHP buildpack does not seem to support the automatic setting of php ini session_save_path variable for redis-sessions services with TLS.
extensions/sessions/extension.py only handles the 'tcp:' scheme.

    def session_save_path(self):
        return "tcp://%s:%s?auth=%s" % (
            self.creds.get('hostname',
                           self.creds.get('host', 'not-found')),
            self.creds.get('port', 'not-found'),
            self.creds.get('password', ''))

To use TLS, the Redis 'uri' specification indicates that the ‘uri’ parameter could be set with scheme ‘rediss://’ instead of ‘redis://’.
This 'uri' parameter could be initialized in the json binding credentials configuration provided by the service broker.
Here's a proposal PR for managing redis-session with TLS

• I have viewed signed and have submitted the Contributor License Agreement
  Go an error at link Individual CLA : Error 404 Not Found 😟

• I have made this pull request to the master branch

• I have added an integration test

[linux-foundation-easycla]

• ✅login: atgitwk / (60abd86)

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[atgitwk]

Hi team
My PR is still in pending review but cloudfoundry/wg-app-runtime-interfaces-buildpacks-php-approvers returns HTTP 404 "Page not found" 😞
Is this normal ?
May anyone help ?