remove auto-adding v to the etcd image version

[xmlking]

Please read https://github.com/coreos/etcd-operator/blob/master/CONTRIBUTING.md#contribution-flow

1. feat(tag): remove auto-adding v to the etcd image version
2. feat(policy): add option to configure HostNetwork and DNSPolicy

[xmlking]

@Marlinc following are source for the above PR.
they are very important changes for my workplace environment where they have enabled Pod Security policies and CNI. I tested then @ workplace and works as expected, Hope you will merge PR.
coreos#2079
coreos#2094

[Wouter0100]

Thanks for the PR! We'll have a look.

[Wouter0100]

I've checked, could you please split the code in multiple merge requests? This merge request contains a lot of changes, mostly irrelevant to the MR itself.

Thanks for the time and the effort.

[Marlinc]

Merged in 125c141