[qca-nss-clients] Register notification chain for openvpn linux tunnel events

Register notification chain for openvpn linux tunnel up and down events.
NSS OpenVPN tunnel device flags will be changed to reflect the same.

Change-Id: I280ebf6a341cf8d332ee5a2c0731f1da26bbcf81
Signed-off-by: Sourav Poddar <souravp@codeaurora.org>
2 files changed