[RFE] Add a squid proxy

[Michele Baldessari]

So while doing Liberty->Mitaka testing I need to to replace the repos from liberty to mitaka and then
run various yum commands from each overcloud node.

As it happens, be it trunk.rdoproject.org, be it the network where this servers are, be it the centos
mirror system, I get timeouts because things are two slow.

What would be absolutely grand for me is to add a use_proxy={true,false} parameter, which when
set to true would set up a caching squid proxy on the undercloud and then make sure that
all the nodes would have yum set up to use that.

This way if one node is successful in downloading repo metadata and/or packages, the other nodes
can piggyback on that success ;)

[Michele Baldessari (michele)]

Or even better we could use a new use_proxy parameter like this
if it is "true" we set up the proxy on the undercloud, if it is set to a URL it will use
that. That way we could also make use of existing proxy infrastructure easily

[Ronelle Landy (rlandy)]

Under consideration for pike-3.

[Ben Nemec (bnemec)]

This is not a ci request. We already use squid in ci.

[Steven Hardy (shardy)]

I'd like to see this, but instead of configuring a proxy on the undercloud, optionally do it on the virthost, then the data could persist between quickstart runs.

In general quickstart support for proxying and/or locally mirroring things seems fairly fragmented, IMO it'd be great if we could streamline this as it does download a ton of data atm, which is particularly annoying when testing quickstart patches that involve repeatedly re-running quickstart (yes I know there's a working dir, but IME things don't always work unless you clean that, so just mirroring/proxying the downloaded stuff would probably be better IMO)