Use only one buildx command for e2e-test

[code-elinka]

1. Docker buildx cmd can build a multiarch image
   in one run. Use it instead of many commands
2. The hack/push-multiarch.sh script is used for e2e build
   via docker buildx (/root/.docker/cli-plugins/docker-buildx).
   It requires to specify HOME=/root so buildx works as expected.
   See:
   github.com/kubernetes/test-infra/tree/master/config/jobs/image-pushing
   

[code-elinka]

/assign @cezarygerard
/assign @mmamczur

/meow

[k8s-ci-robot]

@code-elinka:

In response to this:

/assign @cezarygerard
/assign @mmamczur

/meow

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[k8s-ci-robot]

@code-elinka: GitHub didn't allow me to assign the following users: mmamczur.

Note that only kubernetes members with read permissions, repo collaborators and people who have commented on this issue/PR can be assigned. Additionally, issues/PRs can only have 10 assignees at the same time.
For more information please see the contributor guide

In response to this:

/assign @cezarygerard
/assign @mmamczur

/meow

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[code-elinka]

/unhold

[cezarygerard]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cezarygerard, code-elinka

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [cezarygerard]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment