Do not ask NEW_TASK flag

When starting a app targeting pre-M for the first time we show the permission
review dialog before going to the actual activity.

I had to add the FLAG_ACTIVITY_MULTIPLE_TASK as otherwise other
permisison controller activities might get reused which is not
desireable.

I did add NEW_TASK, but this was wrong. Forcing a NEW_TASK means that
the result of the opened activity will not be given to the original
caller. This is an API break.

Now I add the FLAG_ACTIVITY_MULTIPLE_TASK only when needed.

There are deeper underlying issues with adding
FLAG_ACTIVITY_MULTIPLE_TASK which will be addressed later in 123541623.

Change-Id: I79564a38fdbc884ea735da6f7899972df83adedb
Fixes: 123707909
Test: - atest CtsAppSecurityHostTestCases:android.appsecurity.cts.PermissionsHostTest