Support local mirrors for fetching third-party packages

[Krzysztof Klimonda]

SF.net has been unstable over the last couple of months, so add support for using local mirrors and use them in CI.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/40180
Submitter: Krzysztof Klimonda (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/40196
Submitter: Krzysztof Klimonda (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/40180
Committed: http://github.com/Juniper/contrail-third-party/commit/bda7d7128d0bd8e08cf12b0a32c9bed984abd09f
Submitter: Zuul v3 CI (<email address hidden>)
Branch: master

commit bda7d7128d0bd8e08cf12b0a32c9bed984abd09f
Author: Krzysztof Klimonda <email address hidden>
Date: Wed Feb 28 21:33:30 2018 +0100

Support local third-party mirror

Add support for local third-party mirrors to speed-up builds and make
them less dependant on the network.

This commit modifies XML schema for packages.xml, changing single <url>
element into a list of <url>'s - they will be tried in succession to
fetch packages from.

Additionally, a small utility ``populate_cache.py'' can be used on
a mirror host to create expected structure and download dependencies from
the internet.

Partial-Bug: #1752521
Change-Id: I1f8f1cab750530da854118ce99e48276ae0b6daf

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/40196
Submitter: Krzysztof Klimonda (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/40196
Committed: http://github.com/Juniper/contrail-packages/commit/5cea32a1f76dffd1b5f1a3b02b58620d13695be6
Submitter: Zuul v3 CI (<email address hidden>)
Branch: master

commit 5cea32a1f76dffd1b5f1a3b02b58620d13695be6
Author: Krzysztof Klimonda <email address hidden>
Date: Thu Mar 1 10:06:55 2018 +0100

Use local third-party source mirror if available

Check if DEB_BUILD_OPTIONS has site-mirror set, and use those instead of
downloading source from the internet.

Change-Id: I9d2213033e8dcca752dbd0ffabc9d6e89f7c2a68
Partial-Bug: #1752521
Depends-On: I1f8f1cab750530da854118ce99e48276ae0b6daf