Having a particle system on a second (not main) camera causes a stall on the main thread.

Reproduction Steps:
1. Build & Run the attached project with Autoconnect Profiler enabled
2. Capture some frames, then pause and start to zoom in on the main thread, at the end of Drawing
3. Observe that at the start of the second Camera.Render there is eventually a stall, with a red marker for "ParticleSystem.ScheduleGeometryJobs"

Expected Result:
Placing a particle system under a non-primary camera should not generate a stall in the main thread.

Reproducible in versions 5.6.1p4 and 2017.1.0b9.