packaging: add all erasure code plugins to RPM packages

It means distributing a few plugins that are only used for unit testing
but it does not use much disk space and this is otherwise harmless.

Explicitly listing which plugins are to be installed is problematic
because some of them (isa for now and maybe more later) are not
available for all architectures. Properly maintaining the list of
plugins to install would therefore mean exactly matching which
architecture has which plugins.

http://tracker.ceph.com/issues/9381 Fixes: #9381

Signed-off-by: Loic Dachary <loic-201408@dachary.org>