Fix runtime with less iterations and more threads

Summary:
This Diff fixes ceres 2.0 update in dev/mode which is noticeably slower.

Unfortunately, in the short-term, we found no other issues than brute-forcing the threads # and the reducing the maximum number of iterations.

Differential Revision:
D45604439

Privacy Context Container: L1124100

fbshipit-source-id: 9c27fbb6ba8f3b0de09b2f7994164248be38fc57

opensfm/test/test_reconstruction_incremental.py

@@ -16,6 +16,8 @@ def test_reconstruction_incremental(
 
     dataset.config["bundle_compensate_gps_bias"] = True
     dataset.config["bundle_use_gcp"] = True
+    dataset.config["bundle_max_iterations"] = 20
+    dataset.config["processes"] = 4
     _, reconstructed_scene = reconstruction.incremental_reconstruction(
         dataset, scene_synthetic.tracks_manager
     )