centos7在upgrade的时候显示：Delta RPMs disabled....详见内容？
错误信息在第6行，从代码行开始数，空行不算。
即： Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
前面有其他安装信息，太多，略去
.......
Install 1 Package
Upgrade 66 Packages
Total download size: 104 M
Is this ok [y/d/N]: y
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
lvm2-2.02.115-3.el7_1.1.x86_64.rpm | 897 kB 00:00:52
gnutls-3.3.8-12.el7_1.1.x86_64.rpm | 662 kB 00:02:07
kernel-tools-libs-3.10.0-229.14.1.el7.x86_64.rpm | 1.3 MB 00:00:45 ...
kernel-tools-libs-3.10.0-229.14.1.el7.x86_64.rpm | 591 kB 00:00:32 ...
openldap-2.4.39-7.el7.centos.x86_64.rpm | 233 kB 00:00:36 ...
openldap-2.4.39-7.el7.centos.x86_64.rpm | 195 kB 00:00:33 ...
coreutils-8.22-12.el7_1.2.x86_64.rpm | 0 B 00:00:30 ...
coreutils-8.22-12.el7_1.2.x86_64.rpm
......
后面有其他安装信息，太多，略去
