added userDrop to get rid of newly made $APP mongodb username

Added:

mongo $mongodb_public_ip:$mongodb_port/$mongodb_database --quiet -u admin -p"$admin_pass" --authenticationDatabase="admin" --eval "db.dropUser(\"${APP}\")"

to counter the:

mongo $mongodb_public_ip:$mongodb_port/$mongodb_database --quiet -u admin -p"$admin_pass" --authenticationDatabase="admin" --eval "db.createUser({user: \"${mongodb_username}\", pwd: \"${mongodb_password}\", roles : [{ role : \"dbOwner\", db: \"${mongodb_database}\"}] })"