Shrink size of spark_integration Docker container

[asfimport]

I would like to propose a few changes to the spark_integration Dockerfile:

https://github.com/apache/arrow/tree/master/dev/spark_integration

The size of the resulting image can be reduced by making the following changes:

• consolidating all RUN commands into a single RUN layer (reducing the number of layers)

• running apt-get clean to clear out the package cache

• running conda clean --all to clear out cached package tarballs, abandoned package versions, and other build artifacts from all the libraries that are conda installed

  I will be submitting a PR on GitHub shortly. Generating this issue first so I can tag my PR to it.

Reporter: James Lamb / @jameslamb
Assignee: James Lamb / @jameslamb

PRs and other links:

• GitHub Pull Request #1787

_{Note: This issue was originally created as ARROW-2350. Please see the migration documentation for further details.}

[asfimport]

Uwe Korn / @xhochy:
Issue resolved by pull request 1787
#1787