Update Swagger to 1.6.2 and Maven Swagger Plugin to 3.1.7

[eolivelli]

Motivation

In out build environment (MagNews.com) we are upgrading Swagger to 1.6.2, as it is also used by Pulsar Builder system we would like to upgrade Swagger here as well.
Even if Swagger is used for documentation, swagger-core is a runtime dependency so it is better to guarantee that Pulsar is working well with latest version of Swagger 1.X.

I am also upgrading the Maven Swagger Plugin to 3.1.7, the 3.1.8 is buggy and it fails the build with NPE (the same problem occurs even in MagNews build, so it is not related to Pulsar itself)

Modifications

• Upgrade Swagger version to 1.6.2
• Upgrade Maven Plugin to 3.1.7

Describe the modifications you've done.

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): yes
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no
• The rest endpoints: no (not directly, but swagger-core is a runtime dependency for the REST endpoint)
• The admin cli options: no
• Anything that affects deployment: no

Documentation

• Does this pull request introduce a new feature? no

[Jennifer88huang-zz]

/pulsarbot run-failure-checks

[eolivelli]

@codelipenghui this patch is good to go :-)
all tests passed