rpm: do not always remove compatible symlink during upgrading

[kenhys]

Before:

v4 => v5 => upgrading... it will remove cpmpatible symlinks => v5.x

After:

v4 => v5 => upgrading... do not remove compatible symlinks => v5.x

[kenhys]

Try upgrade from v4 => v5 => v5.

$ sudo yum install -y ./rpmbuild/RPMS/x86_64/fluent-package-5.0.0-2.el7.x86_64.rpm 
Failed to set locale, defaulting to C
Loaded plugins: fastestmirror
Examining ./rpmbuild/RPMS/x86_64/fluent-package-5.0.0-2.el7.x86_64.rpm: fluent-package-5.0.0-2.el7.x86_64
Marking ./rpmbuild/RPMS/x86_64/fluent-package-5.0.0-2.el7.x86_64.rpm as an update to fluent-package-5.0.0-1.el7.x86_64
Resolving Dependencies
--> Running transaction check
---> Package fluent-package.x86_64 0:5.0.0-1.el7 will be updated
---> Package fluent-package.x86_64 0:5.0.0-2.el7 will be an update
--> Finished Dependency Resolution

After upgrading, compatible symlink was kept.

$ ls -la /usr/sbin/td-agent*
lrwxrwxrwx. 1 root root 17 Jul 27 04:56 /usr/sbin/td-agent -> /usr/sbin/fluentd
lrwxrwxrwx. 1 root root 20 Jul 27 04:56 /usr/sbin/td-agent-gem -> /usr/sbin/fluent-gem

After removing fluent-package, symlink was removed (expected).

$ sudo yum remove fluent-package.x86_64 
Failed to set locale, defaulting to C
$ ls -la /usr/sbin/td*
ls: cannot access /usr/sbin/td*: No such file or directory

[daipom]

LGTM. Thanks!