Move findutils requires into libsolv-tools-base

[dcermak]

repo2solv requires find, but it is now part of tools-base

[mlandres]

[master]SUSE:tools (0)> repo2solv /Local/Repo >/dev/null 
/usr/bin/find: No such file or directory
find: exit status 1
[master]SUSE:tools (0)> 
                    ^ $?

And maybe repo2solv should return not-zero. Currently it creates an empty repo cache without indicating the isue.

[dirkmueller]

#569 is an alternative that avoids reintroducing this dependency, thereby keeping the installsize of zypper small.

[mlschroe]

I now implemented the file tree walk in libsolv, so there is no need to relay on an external tool anymore.