Update client_golang dependency to v1.3.0

[KashifSaadat]

What this PR does / why we need it:

Update the prometheus/client_golang dependency to v1.3.0.

On occasion I have experienced the following errors running the ingress nginx controller, causing the container to die and restart:

2020/01/13 14:49:06 http: superfluous response.WriteHeader call from k8s.io/ingress-nginx/vendor/github.com/prometheus/client_golang/prometheus/promhttp.(*responseWriterDelegator).WriteHeader (delegator.go:58)
2020/01/13 14:49:09 Get http+unix://nginx-status/nginx_status: dial unix /tmp/nginx-status-server.sock: connect: connection refused
W0113 14:49:09.053465       8 nginx_status.go:172] unexpected error obtaining nginx status info: Get http+unix://nginx-status/nginx_status: dial unix /tmp/nginx-status-server.sock: connect: connection refused
2020/01/13 14:49:10 Get http+unix://nginx-status/nginx_status: dial unix /tmp/nginx-status-server.sock: connect: connection refused
W0113 14:49:10.152850       8 nginx_status.go:172] unexpected error obtaining nginx status info: Get http+unix://nginx-status/nginx_status: dial unix /tmp/nginx-status-server.sock: connect: connection refused

I haven't been able to consistently reproduce the error through changing load volumes or constructing particular requests, but have hit this on average once every two days. The above issue appears related to prometheus/prometheus#6139, for which there is a potential fix introduced in v1.2.0 of the client_golang dependency.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

How Has This Been Tested?

Ran the unit tests, built ingress-nginx from source with this PR and been running in a test environment (AWS, k8s v1.15) with some example workloads (internal web apps, ELK, Grafana, Artifactory, Sonarqube, Keycloak), haven't seen the issue re-occur (however I also haven't found a method of reliably reproducing this issue unfortunately).

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

[aledbf]

/retest

[aledbf]

/approve

[aledbf]

@KashifSaadat thanks!

[aledbf]

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[aledbf]

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[aledbf]

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[aledbf]

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[aledbf]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, KashifSaadat

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[aledbf]

/retest

[aledbf]

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[aledbf]

/retest