Fix style check issue for ShellCheck.

[junaruga]

This fixes https://github.com/sclorg/rpm-list-builder/issues/106 .

The reason is ShellCheck changed the definition of the check? In my memory, disable=SC2039 was to restrict the use of pushd and popd. Anyway, I fixed, and tested the outdated tests/integration/run.sh script too.

One test case was failed because of the error of "fedpkg srpm" for rh-ror50. Maybe this test script does not follow the feature to add fedpkg.

$ python3 -m venv ./venv

$ source venv/bin/activate

(venv) $ pip install -e .

(venv) $ which rpmlb
~/git/sclorg/rpm-list-builder/venv/bin/rpmlb

(venv) $ sh tests/integration/run.sh 
== TEST: download_only_test ==
  > [OK]

== TEST: download_from_local_and_build_with_dummy_test ==
  > [OK]

== TEST: download_by_rhpkg_and_build_with_dummy_test ==
  > [OK]

== TEST: download_with_custom_and_build_with_dummy_test ==
  > [OK]

== TEST: build_only_verbose_test ==
  > [OK]

== TEST: build_only_with_mock_test ==
  > [FAILURE]

== TEST: build_only_with_custom_echo_test ==
  > [OK]

== TEST: build_only_with_custom_mock_test ==
  > [OK]

== TEST: build_only_resume_test ==
  > [OK]

== TEST: download_and_build_with_custom_echo_test ==
  > [OK]

== TEST: download_and_build_with_custom_mock_test ==
  > [OK]

real    7m29.410s
user    2m50.111s
sys 1m22.038s
exist status: 1

$ vi integration.log
...
2018-04-15 13:38:10,623 ERROR    rpmlb.utils                CMD: [fedpkg srpm] failed at [/home/jaruga/git/sclorg/rpm-list-builder/tmp/work_directory/1/rh-ror50]
...

[junaruga]

Sorry I created the branch to 'origin/hotfix/fix-bash-style` by my mistake. I should create it to my repository.

[junaruga]

I removed ShellCheck and the related code. Could you check and merge? Thanks.

[junaruga]

Thanks for the merging and deleting the remote branch.