Fix package naming in spec file.
Fix package naming in spec file.

The SRPM must remain python-blivet since that's the name of the
package in the fedora pkgdb. We just make the base package
contain no files so the only rpm produced is python3-blivet.

AdamWill/blivet,vojtechtrefny/blivet,vpodzime/blivet,rvykydal/blivet,AdamWill/blivet,vojtechtrefny/blivet,rhinstaller/blivet,jkonecny12/blivet,rhinstaller/blivet,vpodzime/blivet,jkonecny12/blivet,rvykydal/blivet