Mathjax should be used after complete loading

Student couldn't able to submit his answer in ie9
becuase mathjax was used before its complete loading
thats cuase the problem. Mathjax operations should be
handled synchronously inorder to avoid error.

BLD-1199
Merge pull request #4910 from mlkwaqas/waqas/bld1199-mathjax-error

MaxJax error while submitting answer