Extend XML unicode test coverage

Extends the coverage of the servers XML serialization test to
cover unicode values. Fixes common function to be handle fields
being unicode. No actual bug fix, but this is test coverage which
we always should have had, and an investigation into another unicode
bug revealed the missing coverage and problem with the tests
not handling unicode values.

Change-Id: I6255ad1cf9a3429c0d87cb6709c11c1b65df9ba5
Related-Bug: 1279172
Merge "Extend XML unicode test coverage"