Fix pkg_set command for REPONAME attr.
Fix pkg_set command for REPONAME attr.

Reponame attr should not set repo url, as repo url is a separate
package attribute.

Open343/pkg,skoef/pkg,khorben/pkg,junovitch/pkg,khorben/pkg,Open343/pkg,skoef/pkg,en90/pkg,khorben/pkg,en90/pkg,junovitch/pkg