Queue data for multiple requests while single mode launching

Queue data for multiple requests while single mode launching

- It launches only once for single mode. If another request comes while
it's running, store the next and show them in order. And returns all responses
when popup dies as it has been.

- If the number of requested popup exceed max popup number then ignore
new request. In normal situation, it will not exceed the max popup
number because the askuser throw exception for duplicated requests.

Change-Id: Ib7679dec6338a030bd5b90ca39b854bbc02b314a
Signed-off-by: Yunjin Lee <yunjin-.lee@samsung.com>