Fixing shellcheck warnings in entry.sh

[pswica]

Please see: #742 and #726 for more details and context.

Some extra notes:

1. Shellcheck failed when the shebang was #!/bin/sh due to constructs like declare and arrays not existing in POSIX shell.
2. I found that our build container, fedora 24, has bash
3. This, and our new standard drifting toward having #!/usr/bin/env bash, prompted my changes.

[k8s-ci-robot]

@pswica: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pull-release-verify	ea00a38	link	/test pull-release-verify

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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. I understand the commands that are listed here.

[justaugustus]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: justaugustus, pswica

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:

• rpm/OWNERS [justaugustus]

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