Revert "add yum module downgrade support"

This reverts commit cbd1da6457.

library/packaging/yum

@@ -29,7 +29,6 @@ import yum
 try:
     from yum.misc import find_unfinished_transactions, find_ts_remaining
     from rpmUtils.miscutils import splitFilename
-    from rpmUtils.miscutils import compareEVR
     transaction_helpers = True
 except:
     transaction_helpers = False
@@ -40,7 +39,7 @@ module: yum
 version_added: historical
 short_description: Manages packages with the I(yum) package manager
 description:
-     - Installs, upgrades, downgrades, removes and lists packages and groups with the I(yum) package manager.
+     - Installs, upgrade, removes, and lists packages and groups with the I(yum) package manager.
 options:
   name:
     description:
@@ -464,8 +463,6 @@ def install(module, items, repoq, yum_basecmd, conf_file, en_repos, dis_repos):
     res['rc'] = 0
     res['changed'] = False
 
-    downgrade = False
-
     for spec in items:
         pkg = None
 
@@ -540,32 +537,12 @@ def install(module, items, repoq, yum_basecmd, conf_file, en_repos, dis_repos):
             if found:
                 continue
 
-            # downgrade - the yum install command will only install or upgrade to a spec version, it will
-            # not install an older version of an RPM even if specified by the install spec. So we need to
-            # determine if this is a downgrade, and then use the yum downgrade command to install the RPM.
-            split_pkg_name = splitFilename(spec)
-            # if the Name and Version match a version was not provided and this is not a downgrade.
-            if split_pkg_name[0] != split_pkg_name[1]:
-                pkg_name = split_pkg_name[0]
-                pkgs = is_installed(module, repoq, pkg_name, conf_file, en_repos=en_repos, dis_repos=dis_repos, is_pkg=True)
-                if pkgs:
-                    (cur_name, cur_ver, cur_rel, cur_epoch, cur_arch) = splitFilename(pkgs[0])
-                    (new_name, new_ver, new_rel, new_epoch, new_arch) = splitFilename(spec)
-
-                    compare = compareEVR((cur_epoch, cur_ver, cur_rel), (new_epoch, new_ver, new_rel))
-                    if compare > 0:
-                        downgrade = True
-
             # if not - then pass in the spec as what to install
             # we could get here if nothing provides it but that's not
             # the error we're catching here
             pkg = spec
 
-        operation = 'install'
+        cmd = yum_basecmd + ['install', pkg]
-        if downgrade:
-            operation = 'downgrade'
-
-        cmd = yum_basecmd + [operation, pkg]
 
         if module.check_mode:
             module.exit_json(changed=True)