Add the missing XML to byte array conversion method.
While there,
1. Fix writeByteArrayXml method to store the hex chars of the value.
2. Cleanup couple of error strings in |readThisIntArrayXml| method.
BUG: 29039296
Change-Id: I6386f7df7c5c8b7bc3bc5a268196da617209cea9
TEST: Compiles & manual testing.
(cherry picked from commit 651209b597734d34768fbb69ebf982b483167fd5)