Adds XML namespace example for disk config extension

Adds XML namespace and specifying of the disk config value
to the disk config extensions api sample test data for server
creation. This is being done so the api samples used by the
documentation contain the example of this usage.

DocImpact

Change-Id: Icd7aa3743f71dd1cb8575605e5f1ce5da6bd37bf
Closes-Bug: 1189817
Fix type mismatch errors in NetworkTestCase

A few tests of NetworkTestCase use string literals as
network_id values. This works great when running tests
on both SQLite and MySQL, but fails on PostgreSQL, which
is very string when checking data types.

Blueprint: db-api-tests-on-all-backends

Change-Id: I090e42ff045379ac404e7bc5c91fbc82a52920b0
Merge "Adds XML namespace example for disk config extension"
Merge "Fix type mismatch errors in NetworkTestCase"