[owm] make more robustnes, some cleanups
[owm] fix ip6 neighbors
[owm] add ula_prefix

(cherry picked from commit b19f68f4950abd857ae9b5dd5dfc4c9145d595de)
[owm] use ubus for ula_prefix

(cherry picked from commit 7c6c26ba9f96a3ace81195cd90fbd25e35b66db5)
[luci-app-owm] add api_rev
(cherry picked from commit 914a02e6336106042a7695f14862e4b9d9cd4490)
[owm] fix ipv6 ipv4 detection

(cherry picked from commit 442e6d475f5a4d5621facb6f9c5dfffd2d021b3f)
[owm] fix ipv6 device and addr detection

(cherry picked from commit a517895042bf8aa2321ce09f51a3a3978cf62544)