Canonicalize XML strings before comparing to reduce flakiness. am: 974286e087 am: e0f3789531 am: bf4df6abbf am: 4709c07234

Original change: https://android-review.googlesource.com/c/platform/tools/treble/+/1681545

Change-Id: I508b2eee1ceb3db2fdb081edff9ad4d089d990d7