fix(test): Fix the 'Unexpected error' flash in the sign_in tests.

@vladikoff or @zaach - could you guys check this one out? The solution is a hack and only sidesteps the issue of the XHR request being open or the error message being reported as visible. Any help would be appreciated!

This is a dirty hack to avoid a timing problem that causes
an 'Unexpected Error' to be displayed in the 'sign in verified
with password that incorrectly has leading whitespace' test.
The XHR request for the signin request can still be open when the test
completes. If the test finishes immediately, the page redirect closes
the XHR request and flashes an 'Unexpected Error' while waiting
for the next page load.

Also removed duplicate reset password tests, and moved one test from sign_in.js to reset_password.js

fixes #1875