Redis session driver does not support TLS connections

[Ddog800]

TLS connections for Redis are often required for compliance reasons (as I'm currently dealing with myself). While the underlying phpredis extension does support TLS connections by including tls:// in the host string, it appears that the CI Redis session driver does not properly parse TLS connection strings when input into the application session config, causing the app to bomb.

After a bit of testing, this appears to be resolvable with a slight tweak to the Regex matching on the value of $this->_config['save_path'] in the Redis session driver library constructor to ensure that tls:// is matched and included in the first capture group. That will then allow a full host string of, i.e., tls://myrediscache.amazonaws.com to be passed along to the underlying phpredis functions.

[Ddog800]

Opened PR #5983 to implement this change.