Fix AO SAM2 issues (#2109)

Fix AO SAM2 issues (#2109)

Summary:
Pull Request resolved: #2109

SAM2 issues
- Whenever ```clear_old_points``` was enabled SAM2 would crash
AAS Track mult issues
- Enables ```multimask``` flags

Rootcaused issues to failed assertion in the following lines in ```sam2_base.py::_track_step:L788```:

```
            if prev_sam_mask_logits is not None:
                assert point_inputs is not None and mask_inputs is None
                mask_inputs = prev_sam_mask_logits
            multimask_output = self._use_multimask(is_init_cond_frame, point_inputs)
            assert mask_inputs is None
```
Whenever ```prev_sam_mask_logits``` has a value it results in a crash. There are several situations where this is expected to be the case including during streamed runs, or when clearing points.

Test Plan:
aistudio test local aas_track_mult

```
Retrieving package values for `fbcode//ai_demos/server_model_zoo/models/aas_track_mult`:
 buck2 audit package-values --reuse-current-config fbcode//ai_demos/server_model_zoo/models/aas_track_mult
Buck command to find test owners:
 buck2 uquery --reuse-current-config owner(/data/sandcastle/boxes/fbsource/fbcode/ai_demos/server_model_zoo/models/aas_track_mult/test_aas_track_mult_model.py) -a labels
Buck command to invoke a test:
 buck2 test --reuse-current-config --write-build-id /tmp/.tmpS35tJk --client-metadata language=python --client-metadata id=testify.codelens --client-metadata session_id=d0229502-10cc-45e7-a6f6-6c5c276c2e17 fbcode//ai_demos/server_model_zoo/models/aas_track_mult:tests -- --regex ai_demos/server_model_zoo/models/aas_track_mult:tests \- .*(?:\(.*TestAasTrackMultModel\)$|TestAasTrackMultModel: .*) --run-disabled
Buck UI: https://www.internalfb.com/buck2/bf9cbfaa-ae6a-4568-876c-0b128dd474bd
Test UI: https://www.internalfb.com/intern/testinfra/testrun/6473924727918606
Network: Up: 0B  Down: 0B  (reSessionID-8b7877b7-4cf8-4850-ac7b-ee84571b005d)
Command: test.
Time elapsed: 1:07.6s
Tests finished: Pass 4. Fail 0. Fatal 0. Skip 0. Build failure 0
```

Differential Revision: D73460163

Pulled By: jlbmorales

Author: jlbmorales

torchao/_models/sam2/modeling/sam2_base.py

@@ -788,9 +788,10 @@ def _track_step(
             if prev_sam_mask_logits is not None:
                 assert point_inputs is not None and mask_inputs is None
                 mask_inputs = prev_sam_mask_logits
+            else:
+                assert mask_inputs is None
             multimask_output = self._use_multimask(is_init_cond_frame, point_inputs)
 
-            assert mask_inputs is None
             assert multimask_output
             if point_inputs is not None:
                 point_inputs = {k: point_inputs[k].contiguous() for k in point_inputs}