Create DHCP port for IPv6 subnet

There is a bug in dhcp agent code that when first port is created
in an IPv6 subnet, DHCP port is not automatically created.

This fix resolves this problem by removing the IP version check
in configure_dhcp_for_network method.

Change-Id: If3f405d367a7099d9f33d72d11ffcb7a393abe23
Closes-Bug: #1367500
(cherry picked from commit 1b66e11b5d8c0b3de0610ca02c3e10b6f64ae375)
Big Switch: Fix SSL version on get_server_cert

The ssl.get_server_certificate method uses SSLv3 by default.
Support for SSLv3 was dropped on the backend controller in
response to the POODLE vulnerability. This patch fixes it
to use TLSv1 like the wrap_socket method.

Closes-Bug: #1384487
Change-Id: I9cb5f219d327d62168bef2d7dbee22534b2e454e
(cherry picked from commit 77e283c94f51e21dcf126a316098c54a7cdfca0f)
Fix sleep function call

Remove time.sleep method reference in class and use time.sleep directly.

Change-Id: Ib4c02061b29c0d584d603746a78ab50922f781c3
Closes-Bug: 1375698
(cherry picked from commit 8e36ba8d24c198cb5e6c0e4ddc29a08904e3e10c)
Merge "Create DHCP port for IPv6 subnet" into stable/juno
Merge "Big Switch: Fix SSL version on get_server_cert" into stable/juno