centos 下yum lock的解决办法
centos7下yum install的时候，报了一堆错误，如下：
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 38 M RSS ( 37 MB VSZ)
Started:Sta Jul 24 16:28:58 2010 - 1:37:07 ago
State : Sleeping, pid: 13020
解决办法:
rm -f /var/run/yum.pid