fix the problem "yum rpmdb open failed" when installing apps on CentOS 7

when trying to install applications on CentOS, you may get some errors like something below: 在centos系统上，在使用yum命令安装软件包时候报错： rpmdb: Thread/process 35884/139793484506880 failed: Thread died in Berkeley DB library error: db3 error(-30974) from dbenv->fai...