Incognito Mode Add Tab button should open a new tab

Incognito Mode Add Tab button  should open a new tab

[Issue] https://bugs.tizen.org/jira/browse/TT-221
[Problem] Incognito mode Add Tab button doesn't create new tab
[Solution] IncognitoMode always opens a new tab.
[Verification]
1) Open Tab Manager
2) Add Incognito Tab
3) Type url address and press Enter

2 -> New tab should be opened.
3 -> site should be opened in the current tab.

1) Open Tab Manager
2) Add Incognito Tab
3) Press BookmarkManager and click bookmark

3-> site should be opened in the current tab.

Change-Id: I7e2d98bbba1a2d5bc09afe8b4a4f5d055c2724c2