32bit パッケージバージョンをインストールできず Multilib version problems found エラーが発生する

Issue

• 既存のパッケージ (つまり pam.x86_64) の 32bit バージョンをインストールしようとすると、以下のエラーが発生します。

# yum install pam.i686
Loaded plugins: product-id, rhnplugin, security, subscription-manager
This system is receiving updates from RHN Classic or RHN Satellite.
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package pam.i686 0:1.1.1-20.el6_7.1 will be installed
--> Processing Dependency: libaudit.so.1 for package: pam-1.1.1-20.el6_7.1.i686
--> Processing Dependency: libcrack.so.2 for package: pam-1.1.1-20.el6_7.1.i686
--> Running transaction check
---> Package audit-libs.i686 0:2.3.7-5.el6 will be installed
---> Package cracklib.i686 0:2.8.16-4.el6 will be installed
--> Finished Dependency Resolution
Error:Multilib version problems found.This often means that the root
       cause is something else and multilib version checking is just
       pointing out that there is a problem.Eg.:

         1.You have an upgrade for pam which is missing some
            dependency that another package requires.Yum is trying to
            solve this by installing an older version of pam of the
            different architecture.If you exclude the bad architecture
            yum will tell you what the root cause is (which package
            requires what).You can try redoing the upgrade with
            --exclude pam.otherarch ... this should give you an error
            message showing the root cause of the problem.

         2.You have multiple architectures of pam installed, but
            yum can only see an upgrade for one of those arcitectures.
            If you don't want/need both architectures anymore then you
            can remove the one with the missing update and everything
            will work.

         3.You have duplicate versions of pam installed already.
            You can use "yum check" to get yum show these errors.

       ...you can also use --setopt=protected_multilib=false to remove
       this checking, however this is almost never the correct thing to
       do as something else is very likely to go wrong (often causing
       much more problems).

       Protected multilib versions: pam-1.1.1-20.el6_7.1.i686 != pam-1.1.1-13.el6.x86_64