fix deadlock during join while map load happens. fixes #2530 , #3033
migration check is removed since it is unneccessary because we are already migrating partition loaded flag as true.Also has some test improvements
get rid of the sleep calls in the test
Merge pull request #3045 from eminn/fix/map-store-deadlock

fix deadlock during join while map load happens. fixes #2530 , #3033