Making assert_repo_reset test more resilient to git versions.

Fedora 19:

[root@broker tmp]# git clone --bare --no-hardlinks git://github.com/openshift/downloadable-mock.git AppRepoFuncTest.git
[root@broker tmp]# cd AppRepoFuncTest.git
[root@broker AppRepoFuncTest.git]# git config core.logAllRefUpdates true
[root@broker AppRepoFuncTest.git]# git reset --soft 'HEAD~1'
[root@broker AppRepoFuncTest.git]# git reflog | head -1
e7bbb95 HEAD@{0}: reset: moving to HEAD~1

RHEL 6.4:

[root@broker tmp]# git clone --bare --no-hardlinks git://github.com/openshift/downloadable-mock.git AppRepoFuncTest.git
[root@broker tmp]# cd AppRepoFuncTest.git/
[root@broker AppRepoFuncTest.git]# git config core.logAllRefUpdates true
[root@broker AppRepoFuncTest.git]# git reset --soft 'HEAD~1'
[root@broker AppRepoFuncTest.git]# git reflog | head -1
e7bbb95 HEAD@{0}: HEAD~1: updating HEAD
Merge pull request #3087 from kraman/bugfix

Merged by openshift-bot