Better support of gpg keys installation behind a proxy

[paolomainardi]

Building the base image from scratch starting from the source in a proxied environment, it can cause issues using gpg to import keys, this MR address the issue by changing the gpg host port to 80 and adding the protocol.

Refs: https://unix.stackexchange.com/questions/75892/keyserver-timed-out-when-trying-to-add-a-gpg-public-key

[chorrell]

LGTM!

And it looks like this might solve the random timeouts and failures we've seen in Travis-CI when fetching gpg keys. Looking at the test builds for this PR, the builds are faster and there are no delays or retries when fetching the gpg keys:

https://travis-ci.org/nodejs/docker-node/builds/337534011

Previous builds, particularly the failed ones, you see a lot of No route to host errors

[chorrell]

I'm not sure if hkp://ha.pool.sks-keyservers.net:80 actually works.

When I try that locally I get:

$ gpg --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-keys 94AE36675C464D64BAFA68DD7434390BDBE9B9C5
gpg: keyserver receive failed: No route to host

[tianon]

It'll work sometimes -- if you want to use port 80, you have to swap from the "ha" pool to the "p80" pool.

[chorrell]

ah, right, forgot about the p80. I'll do a follow up PR.

[chorrell]

For reference:

$ gpg --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 94AE36675C464D64BAFA68DD7434390BDBE9B9C5
key 7434390BDBE9B9C5:
4 signatures not checked due to missing keys
gpg: key 7434390BDBE9B9C5: "Colin Ihrig <[email protected]>" not changed
gpg: Total number processed: 1
gpg:              unchanged: 1