update redhat-release file in etc

[phillxnet]

As reported by @kcomer in the following forum thread:- https://forum.rockstor.com/t/nosuchpackage-dmraid/1465 the current as of 3.8-13.07 version of /etc/redhat-release contains:-
Rockstor release 3.8.10 (Core)
This should probably reflect the version of Rockstor used for the original install, hence this issue's location in the rockstor-iso repo.
This way we can maintain a knowledge of which iso was used to install a particular install.

Please update the above forum thread with significant development on this issue.

[phillxnet]

Note that as of Rockstor-3.9.0.iso the /etc/rehat-release file (symlink) contains the following:

Rockstor release 3.8.16 (Core)

and we have the following:

ls -la /etc/redhat-release 
lrwxrwxrwx. 1 root root 16 Apr 14 16:23 /etc/redhat-release -> rockstor-release