move login js from js_block to bundle, fixes CNVS-10544

because we added a dependency (see 130a1506) that wasn't in the common
bundle, the require in the js_block became asynchronous and would run
after the custom account js (r.js doesn't optimize js_blocks)

test plan:
1. use the following custom account js: http://bit.ly/1j4Js2x
2. go to the login page
3. you should see the custom field placeholders, and no weird overlapping
4. the javascript on the page should work (required fields, forgot
   password, etc.)

Change-Id: I6468f96dbf51f881e69aedb0f9c6968d9da061a0
Reviewed-on: https://gerrit.instructure.com/28765
Reviewed-by: Dan Dorman <ddorman@instructure.com>
QA-Review: Marc LeGendre <marc@instructure.com>
Product-Review: Marc LeGendre <marc@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>