[nicoddemus]

Add hostname and timestamp to JUnit XML testsuite tag

Conflicts:
testing/test_junitxml.py

Requested from #5471 (comment)

[nicoddemus]

OK to merge: the py34 failure on Azure can be ignore, it seems Azure no longer supports Python 3.4:

##[error]Version spec 3.4 for architecture x64 did not match any version in Agent.ToolsDirectory.
Versions in C:/hostedtoolcache/windows:
2.7.16 (x86)
3.5.4 (x86)
3.6.8 (x86)
3.7.5 (x86)
3.8.0 (x86)
2.7.16 (x64)
3.5.4 (x64)
3.6.8 (x64)
3.7.5 (x64)
3.8.0 (x64)

But it passes on Travis so we're good.