Do not set waitForDebugger if the process to be debugged already started

For non-persistent debug settings, mDebugApp and mWaitForDebugger flags
will only be restored when we get attachApplication. If the process is
already running, we can't wait for debugger and there will be no
attachApplication calls coming.

We should leave the settings unmodified, otherwise after two such calls,
both mDebugApp and mOrigDebugApp will point to the same app, and the
debug settings can never be restored.

bug: 27931552
Change-Id: Id53e21bbe154f45bf2ca12bb5d7fd56279bae653