Provide a way for "spk dev" to disable adding to sandstorm-files.list

[paulproteus]

Context: App developers would appreciate a way to (feel like they are) SSH-ing in to a Sandstorm grain, while it is running, so they can poke around and figure out what is going on.

Summary: spk dev should have a way to disable tracing. I'm filing this against the sandstorm repo since I believe it would take some kind of change for spk or sandstorm to make this work.

Steps to reproduce

• Run vagrant-spk dev
• Create a grain
• Use the following commands to gain shell access to the grain:

vagrant-spk ssh
cd /opt/app/.sandstorm
sudo nsenter --target $(pidof sandstorm-http-bridge) --wd --mount --net --ipc --uts --pid

• Run some commands to figure out what is going on within the grain, so you can fix the packaging scripts.

Expected results

Operations performed during the nsenter do not not modify sandstorm-files.list since it is intended for debug use.

Actual results

Doing this results in a bigger sandstorm-files.list.

[kentonv]

This should go along with an spk sh command (or something) that rendezvous with spk dev, tells it to disable tracking temporarily, then runs a shell in the namespace. After exiting, it tells spk dev to resume tracking.