Remove duplication of Dns in config merging.

Fixes #4714
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
rename lxc to bridge

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Fix since time exit display when s.FinishedAt is zero

When s.FinishedAt is zero, the since time exit in docker ps doesn't display correct time.
For example
```
Exited (0) 292.471209 years ago
```
This patch fixes the since time exit to display nothing if s.FinishedAt is zero.

Docker-DCO-1.1-Signed-off-by: Ken ICHIKAWA <ichikawa.ken@jp.fujitsu.com> (github: ichik1)
Merge pull request #4761 from ichik1/fix-display-of-since-time-exit

Fix since time exit display when s.FinishedAt is zero
Merge pull request #4800 from vieux/rename_network_driver

rename lxc to bridge
Merge pull request #4775 from LK4D4/remove_duplicate_dns_#4714

Remove duplication of Dns in config merging.