Ignore "no such file" error when docker cannot find `resolv.conf`
Ignore "no such file" error when docker cannot find `resolv.conf`

`/etc/resolv.conf` is not an essential file in filesystem. (see
http://man7.org/linux/man-pages/man5/resolv.conf.5.html)

> If this file does not exist, only the name server on the local machine
> will be queried

It's baffling to users that containers can start with an empty
`resolv.conf` but cannot without this file.

This PR:
* ignore this error and use default servers for containers in `bridge`
  mode networking.
* create an empty resolv.conf in `/var/lib/docker/containers/<id>` in
  `host` mode networking.

Signed-off-by: Yuanhong Peng <605597f567e7188f3c817a57f8e09c6e857f9d0b@huawei.com>

jameszhan/docker,vdemeester/docker,trebonian/docker,jimjag/docker,Mokolea/docker,jthelin/docker,flavio/docker,flavio/docker,konstruktoid/docker-upstream,djs55/docker,jthelin/docker,AkihiroSuda/docker,bearstech/moby,docker/docker,Ramzec/docker,mahak/docker,moul/docker,moby/moby,Ramzec/docker,bearstech/moby,AkihiroSuda/docker,flavio/docker,trebonian/docker,AkihiroSuda/docker,gnailuy/docker,nalind/docker,Mokolea/docker,Ramzec/docker,Mokolea/docker,gnailuy/docker,jimjag/docker,yosifkit/docker,mahak/docker,djs55/docker,bearstech/moby,moby/moby,moul/docker,moby/moby,cpuguy83/docker,gnailuy/docker,nawawi/docker,Ramzec/docker,yosifkit/docker,moul/docker,nawawi/docker,docker/docker,thaJeztah/docker,djs55/docker,jameszhan/docker,yosifkit/docker,nalind/docker,nalind/docker,vdemeester/docker,mahak/docker,paralin/docker,paralin/docker,nalind/docker,trebonian/docker,nawawi/docker,cpuguy83/docker,moul/docker,jameszhan/docker,thaJeztah/docker,flavio/docker,jimjag/docker,mahak/docker,konstruktoid/docker-upstream,thaJeztah/docker,thaJeztah/docker,moby/moby,Mokolea/docker,nawawi/docker,AkihiroSuda/docker,vdemeester/docker,docker/docker,bearstech/moby,konstruktoid/docker-upstream,trebonian/docker,paralin/docker,yosifkit/docker,cpuguy83/docker,konstruktoid/docker-upstream,cpuguy83/docker,paralin/docker,gnailuy/docker,jimjag/docker