Missing RPM dependency on package "hostname" for Galera

To conduct SST, Galera calls a shell script /usr/bin/wsrep_sst_common, which in turn invokes the hostname binary. However, the RPM package for Galera does not have a dependency on the "hostname" RPM package. As a result, Galera refuses to start on a system that lacks this package.

While "hostname" is a basic RPM package that is usually installed by default, minimalistic environments (like containers) often lack it. A good practice for an RPM package is to require all the packages or binaries it will need and let YUM resolve the dependencies. Therefore, either "hostname" (which will be resolved to a package name) or "/bin/hostname" (which will be resolved as a binary) should be listed as dependency ("Require:" line) in the Galera RPM spec file.

It is quite likely that the DEB packages we provide suffer from the same deficiency.

These changes should also be propagated to the ES.