Revert "We force the use of https; but dont require the mod_ssl pacakge....

..."

Commit d95628420b6f73de6d86f4c37f72e9bfb3a256fc removed the "requires
mod_ssl" line because what cobbler needs is an ssl enabled httpd
server, *NOT* mod_ssl, and in particular (free)ipa uses mod_nss
to provide ssl services. So, over time expect to see far more
systems using mod_nss rather than mod_ssl.

Cobbler works fine with mod_nss or mod_ssl, but mod_nss and mod_ssl
conflict, *both* cannot be installed. As rpm has no mechanism to
specify "either/or" conditions, the only solution is to specify
neither.

This reverts commit 1e731294d148e729c1064b0fd53b037a82cf0386.