Add waiting to test to wait for the Workspace to be in Edit mode

I thought I wouldn't need to wait for the Edit mode to start but
sometimes the test goes too fast and drops the item before we get
to the edit mode and the drop doesn't have the correct coordinates
or get's cancelled.

Fix: 352569050
Test: IntegrationReorderWidgetsTest
Flag: TEST_ONLY
Change-Id: I744579c28267189f85b9ca297e1d170d6120bb64