Starting multiple gcsfuse processes using PAPI action list

[samanvp]

In the latest version of DeepVariant (0.8.0) gcsfuse binary has been removed from the docker image. In order to be able to run make_example on multi core machines we still need to start multiple gcsfuse processes (one per core). We achieve this by launching PAPI using a json file that includes action list in the following order:

• mkdir local directories for gcsfuse
• gcsfuse process 1
• gcsfuse process 2
• ...
• gcsfuse process n
• seq 1 n | parallel make_example

This will be essentially equivalent to what we were doing using DeepVariant 0.7.2

[samanvp]

I ran a bunch of profiling experiments to compare this new implementation of gcsfuse to our current one (which gcsfuse binary exists in deepvariant docker image) and the performance is almost identical.