Audit CoreAPI for cases where the context should be canceled internally

[Stebalien]

Version information:

v0.5.0-rc3

Description:

There are several places in the CoreAPI (e.g., Ls) where we're assuming the context will be canceled when the caller is done. If that doesn't happen, we won't cleanup some resources.

Luckily, we are canceling these contexts. However, we shouldn't require that.

[hsanjuan]

@Stebalien may I ask to associate priority to this, and whether this is Help Wanted (in which case it probably needs difficulty and effort tags).

[Stebalien]

Done.