allow yum to run as non-root user. (#20)

* Update linux_updates.rb

run yum-cli via sudo, so can work with non-root user

* Update linux_updates.rb

set cache dir for yum. Default cache dir needs root access. setting the cache dir to tmp to allow non-root users to run this test. This way we don't need to allow ssh to the root account, or enable python in sudoers.

* Update linux_updates.rb

remove unneeded 'sudo'

Author: iveskins

libraries/linux_updates.rb

@@ -199,7 +199,7 @@ def packages
   def updates
     rhel_updates = <<-PRINT_JSON
 #!/bin/sh
-python -c 'import sys; sys.path.insert(0, "/usr/share/yum-cli"); import cli; list = cli.YumBaseCli().returnPkgLists(["updates"]);res = ["{\\"name\\":\\""+x.name+"\\", \\"version\\":\\""+x.version+"-"+x.release+"\\",\\"arch\\":\\""+x.arch+"\\",\\"repository\\":\\""+x.repo.id+"\\"}" for x in list.updates]; print "{\\"available\\":["+",".join(res)+"]}"'
+python -c 'import sys; sys.path.insert(0, "/usr/share/yum-cli"); import cli; ybc = cli.YumBaseCli(); ybc.setCacheDir("/tmp"); list = ybc.returnPkgLists(["updates"]);res = ["{\\"name\\":\\""+x.name+"\\", \\"version\\":\\""+x.version+"-"+x.release+"\\",\\"arch\\":\\""+x.arch+"\\",\\"repository\\":\\""+x.repo.id+"\\"}" for x in list.updates]; print "{\\"available\\":["+",".join(res)+"]}"'
 PRINT_JSON
     cmd = @inspec.bash(rhel_updates)
     unless cmd.exit_status == 0