CLOUDSTACK-10233: use namespace in Libvirt domain metadata.

[fmaximus]

The documentation of Libvirt specifies the requirement of using an XML namespace,
when having metadata in the Domain XML. The Nuage extenstion metadata was not
adhering to this specification, and the lastest Libvirt version ignores it in that case.

[krissterckx]

Proved to work fine with the specified libvirt version.

LGTM

[smeetsr]

LGTM, verified on top of RHEL7.2 & RHEL7.4

[sgoeminn]

LGTM

[krissterckx]

@rhtyd as exchanged, for inclusion into 4.11.0.0 if there would be a 2nd RC. Thanks!

[rohityadavcloud]

@blueorangutan package

[blueorangutan]

@rhtyd a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

@rhtyd a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

@rhtyd a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

@rhtyd a Jenkins job has been kicked to build packages. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result: ✔centos6 ✔centos7 ✔debian. JID-1659

[rohityadavcloud]

@blueorangutan test

[blueorangutan]

@rhtyd a Trillian-Jenkins test job (centos7 mgmt + kvm-centos7) has been kicked to run smoke tests

[blueorangutan]

Trillian test result (tid-2169)
Environment: kvm-centos7 (x2), Advanced Networking with Mgmt server 7
Total time taken: 24160 seconds
Marvin logs: https://github.com/blueorangutan/acs-prs/releases/download/trillian/pr2410-t2169-kvm-centos7.zip
Intermitten failure detected: /marvin/tests/smoke/test_internal_lb.py
Intermitten failure detected: /marvin/tests/smoke/test_vpc_redundant.py
Intermitten failure detected: /marvin/tests/smoke/test_host_maintenance.py
Smoke tests completed. 67 look OK, 0 have error(s)
Only failed tests results shown below:

Test	Result	Time (s)	Test File

[rohityadavcloud]

Test LGTM, merging based on test results and code reviews.

This PR has been accepted towards 4.11.0.0, and should make into RC2 as it fixes a libvirt domain/vm xml spec issue and may cause issue when users are using nuage integration.