DO NOT MERGE: Fix the display id for testNewTaskSameDisplay

testNewTaskSameDisplay CTS test was looking at the DEFAULT_DISPLAY_ID to
check for an activity which was meant to be checking against a newly
created display.

Bug: 71750967
Testing: Test passes on Walleye on oreo-mr1-cts-dev now.

Change-Id: Ie57829d10859b1245e2233cc31ff92bdc828227c
Signed-off-by: Karthik Ravi Shankar <karthikrs@google.com>