Use "travis_retry" function in some key places to reduce CI flakiness

[asfimport]

There's enough things that can go wrong in our CI due to external package registries that we can often end up with spurious failures not caused by code changes.

For example, here is an NPM registry failure:

https://travis-ci.org/apache/arrow/jobs/277798491#L941

I have seen Maven Central fail or anaconda.org fail in the past, too. Some of these package commands that hit external resources could be wrapped in travis_retry to give them another shot at success

Reporter: Wes McKinney / @wesm

_{Note: This issue was originally created as ARROW-1583. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
This is being done already in many places, suggest opening issues to address particular flakiness that we see periodically