Description of problem:

yum is not honoring the preferred hardware architecture when updating packages.  For example, repository containing:

	===========================================
	Package  Arch   Version     Repository
	===========================================
	dummy.x86_64     1-1        testrepo
	dummy.i686       1-2        testrepo

Yum will install dummy-1-2.i686 because the version is newer, even though the x86_64 version is already installed.

This is true even when /etc/yum.conf has the following directives set:

	exactarch=1
	multilib_policy=best
	protected_multilib=1

It is understood that it is bad form to have the package versions/arch out of sync like this.  However, the concern is that in the event that a problem occurred and the repository *accidentally* became out of sync, the expectation is that yum should fail to warn of the issue rather than simply change arch of many packages potentially causing a disruption of service.

	# yum update dummy.x86_64
	testrepo       | 2.9 kB  00:00:00     
	Resolving Dependencies
	--> Running transaction check
	---> Package dummy.x86_64 0:1-1 will be updated
	---> Package dummy.i686 0:1-2 will be an update
	--> Finished Dependency Resolution
	
	Dependencies Resolved
	===================================================================================
	 Package            Arch              Version          Repository             Size
	===================================================================================
	Updating:
	 dummy              i686              1-2              testrepo              1.5 k
	
	Transaction Summary
	===================================================================================
	Upgrade  1 Package

Version-Release number of selected component (if applicable):

	RHEL 7.2
	yum-3.4.3-132.el7.noarch
	rpm-4.11.3-17.el7.x86_64

How reproducible:

Steps to Reproduce:
1.  yum install -y createrepo httpd

2.  systemctl start httpd

3.  Copy attached rpms (dummy-1-1.x86_64.rpm  dummy-1-2.i686.rpm) 
	to /var/www/html/testrepo

4.  Copy attached testrepo.repo into /etc/yum.repo.d/

5.  Add the following directives to /etc/yum.conf
	exactarch=1
	multilib_policy=best
	protected_multilib=1

6.  confirm the test repo configured
	yum repolist 

7.  confirm both packages available from repo
	yum list dummy

8.  Install dummy.  Note that it installs lower versioned, x86_64 package
	yum install dummy

9.  Update dummy.  Note that it installs the higher versioned, i686 package,
    even though x86_64 might be specified.

	yum update dummy.x86_64

Actual results:
Yum upgrades to dummy-1-2.i686.rpm, honoring the version number over the architecture.


Expected results:
	Yum, with the directives configured, would either generate an error or simply 
	not update the package since the $arch is different.
	dummy-1-1.x86_64.rpm would remain installed.


Additional info: