Rejoin a user in IN_PROGRESS match don't let them create new one! And Fix Game not getting removed

[asutosh-147]

if a user has any match in progress and he tries to create a new random match then don't let him create a new random match instead
rejoin him with that inprogress match.

this will ensure that there exists no two matches in games array(inside gameManager class) in which same player is playing simultaneously more than one matches (i.e. no 2 matches in games[ ] will have any common whitePlayerId or blackPlayerId)