ec2/ec2test: set empty DNSName initially

ec2/ec2test: set empty DNSName initially

Initially set empty DNSName, causing the
client to re-request the DNSName. This
exercises the address refreshing logic
in juju's ec2 provider.

https://code.launchpad.net/~axwalk/goamz/ec2test-empty-dnsname/+merge/199466

(do not edit description out of merge proposal)

[axw, 2013-12-18 14:31:08]

Please take a look.

[rog, 2013-12-18 14:39:38]

LGTM with one thought below.

https://codereview.appspot.com/43650045/diff/1/ec2/ec2test/server.go
File ec2/ec2test/server.go (right):

https://codereview.appspot.com/43650045/diff/1/ec2/ec2test/server.go#newcode567
ec2/ec2test/server.go:567: PrivateDNSName:   fmt.Sprintf("%s.internal.invalid",
id),
I wonder if we should do it for these addresses too.

[axw, 2013-12-18 14:55:30]

On 2013/12/18 14:39:38, rog wrote:
> LGTM with one thought below.
> 
> https://codereview.appspot.com/43650045/diff/1/ec2/ec2test/server.go
> File ec2/ec2test/server.go (right):
> 
>
https://codereview.appspot.com/43650045/diff/1/ec2/ec2test/server.go#newcode567
> ec2/ec2test/server.go:567: PrivateDNSName:  
fmt.Sprintf("%s.internal.invalid",
> id),
> I wonder if we should do it for these addresses too.

I can see it could be useful, but I think only if you could control which ones
are empty, or if they're initially all empty and each one is updated on
successive calls.
That's a much bigger change, though, that I'd like to leave to when we need it.