Only check once before re-setting ready priority

Only check once before re-setting ready priority

The macro taskRESET_READY_PRIORITY checks if the task being removed from the
ready list is the last one and only then resets the top ready priority
by calling portRESET_READY_PRIORITY. If we already know that it is the
last ready task being removed then there is no need to perform the check
again and the macro portRESET_READY_PRIORITY can be called directly. We were
doing the unnecessary check at two places and this commit fixes them.

This commit also increases the time period of check task to ensure that all
the demo tasks get a chance to run before the check is performed.