adding read_timeout_override and session_log optional_args for netmiko

[davama]

Similar to https://github.com/napalm-automation-community/napalm-s350/pull/82 but adding the optional_args instead.

[davama]

Please let me know if there is something i need to change

thanks!

[dteslya]

Just came up with the same patch and found your PR. I hope it will be merged eventually.