Frequently in my PC it happens that immediately after starting CentOS 6.5 on process uses yum for whatever reason which I suspect it should be update manager. This could be annoying because nothing appears in the interface and I really have no idea when the process would release yum lock and the situation could be worse when I have something urgent to do with yum. The reason for such a problem for me is unknown and I guess it might be either bug or some misconfiguration in the system.
Anyhow, for solving the problem the only solution I found is to kill the process that holds the lock. Terminating the process is quite easy. If you had paid attention to the terminal result, you would have realized that the PID of the process that holds lock is given to you. Hence, the only thing you need to do is running the following command to kill the process
$ sudo kill -9 [PID Number]
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