Bump version to 1.7.3

[izgeri]

What does this PR do?

Bumps the version to 1.7.3

Also completes some missing updates to bump the Go version to 1.15, including:

• following the instructions here for installing SQL server ODBC driver on Debian 10 in our test automation
• following the instructions here for installing OpenJDK on Debian 10 in our test automation
• updating our certificates used by the generic and MSSQL test automation

What ticket does this PR close?

Resolves #1386

Checklists

Change log

• [x] The CHANGELOG has been updated, or
• [ ] This PR does not include user-facing changes and doesn't require a CHANGELOG update

Test coverage

• [ ] This PR includes new unit and integration tests to go with the code changes, or
• [x] The changes in this PR do not require tests

Documentation

• [x] This PR does not require updating any documentation, or
• [ ] Docs (e.g. READMEs) were updated in this PR, and/or there is a follow-on issue to update docs

(For releases only) Manual tests

• [x] Manually run Kubernetes-Conjur demo with a local Secretless Broker image build of your branch

[codeclimate[bot]]

Code Climate has analyzed commit 86084a46 and detected 2 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Style	2

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 53.6% (0.0% change).

View more on Code Climate.