Bump fluent-bit to 0.15.4

[branden]

What type of PR is this?

Chore

What this PR does/ why we need it:

Update the fluent-bit chart to 0.15.4, and the appversion to 1.7.3.

Which issue(s) this PR fixes:

no issue

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Update to the latest minor version just to keep up with upstream. The bugfixes listed should have no effect on our default configurations.

https://fluentbit.io/announcements/v1.7.0/
https://fluentbit.io/announcements/v1.7.1/
https://fluentbit.io/announcements/v1.7.2/
https://fluentbit.io/announcements/v1.7.3/

Checklist

• The commit message explains the changes and why are needed.
• The code builds and passes lint/style checks locally.
• The relevant subset of integration tests pass locally.
• The core changes are covered by tests.
• The documentation is updated where needed.

[d2iq-mergebot]

This repo has @mesosphere-mergebot integration. You can perform the following commands by submitting a comment. Submit a comment with content "@mesosphere-mergebot help" to view more detailed help text and examples. Be sure the have a look at the mergebot documentation, too.

@mesosphere-mergebot backport  

[joejulian]

@mesosphere-mergebot backport release/3 release/4

[d2iq-mergebot]

Backport PR for release/3: #1052
Backport PR for release/4: #1053
Conflicts present in files:

addons/fluentbit/fluentbit.yaml