14.0.1 rpm throws "docker: command not found" error. Should not.

Summary

A bundled script in the 14.0.1 RPM package expects docker to exist. It should check first before assuming it exists.

/usr/share/gitlab-runner/clear-docker-cache: line 12: docker: command not found

See full below.

Steps to reproduce

Install gitlab-runner 14.0.1 RPM without the docker command present.

Actual behavior

...
Running transaction
  Updating   : gitlab-runner-14.0.1-1.x86_64                                                                                      1/2
GitLab Runner: detected user gitlab-runner
Runtime platform                                    arch=amd64 os=linux pid=2267 revision=c1edb478 version=14.0.1
gitlab-runner: the service is not installed
Runtime platform                                    arch=amd64 os=linux pid=2285 revision=c1edb478 version=14.0.1
gitlab-ci-multi-runner: the service is not installed
Runtime platform                                    arch=amd64 os=linux pid=2370 revision=c1edb478 version=14.0.1
Runtime platform                                    arch=amd64 os=linux pid=2466 revision=c1edb478 version=14.0.1
/usr/share/gitlab-runner/clear-docker-cache: line 12: docker: command not found
  Cleanup    : gitlab-runner-13.12.0-1.x86_64                                                                                     2/2
  Verifying  : gitlab-runner-14.0.1-1.x86_64                                                                                      1/2
  Verifying  : gitlab-runner-13.12.0-1.x86_64                                                                                     2/2

Updated:
  gitlab-runner.x86_64 0:14.0.1-1

Complete!

Expected behavior

No error about docker not being found.

Relevant logs and/or screenshots

Environment description

Used GitLab Runner version

Version:      14.0.1
Git revision: c1edb478
Git branch:   refs/pipelines/326100216
GO version:   go1.13.8
Built:        2021-06-23T16:35:23+0000
OS/Arch:      linux/amd64