In some cases, bound values were setting the flags tracking changes in
gr-account-info. Resetting the flags when loadData is called ensures no
false positives occur.
In addition, upgrades the _usernameChanged logic to compare to the
existing account username value, as opposed to just setting the flag to
true on any modification.
Bug: Issue 7893
Bug: Issue 8287
Change-Id: I75a3cda93bb065a7b9640d4b40905a5e21042bb5
(cherry picked from commit 5cb34e7fa3)
525c98bf3d