Fixed for widget crash when multiple authentication has to be done.

Fixed for widget crash when multiple authentication has to be done.

When the multiple authentication message is sent to WRT,
the crash is occurred after second popup because authenticationChallengeProxy is released.

[Title] Fixed for widget crash when multiple authentication has to be done.
[Issue#] N/A
[Problem] When the multiple authentication message is sent to WRT from webkit, crash is occurred.
[Cause] authenticationChallengeProxy is release after second message.
[Solution] Change the send messgae method to sendSync with delayed option.
[SCMRequest] N/A

Change-Id: Icf1b0d3738759ae2f54137ba852eca1d873215ac