Apparently the /usr/lib/sendmail link was removed recently from the sendmail package because alternatives is supposed to provide it, but the version of alternatives I'm running doesn't. I think sendmail's RPM needs to have a dependency on the version of chkconfig (or later) in which the link was first introduced.
What exactly have you done to get the error? It works for me without any problem.
Perhaps that's because you don't have anything installed on your system which assumes that /usr/lib/sendmail exists. I have such scripts installed on my system, and they stopped working when I installed the new sendmail RPM because /usr/lib/sendmail was removed from it. There was no "error" per se, just the disappearance of a program from a standard location.
Please use system-switch-mail and switch to sendmail again. The link will be there, then. /usr/lib/sendmail is a symlink for copatibility reasons. Newer programs should not use it anymore.
System-switch-mail solved the problem, but this does not change the fact that upgrading sendmail made the link go away. You need to do something in the postinstall scripts to refresh the alternatives mta state to get it to recreate the link. Otherwise you're breaking people's systems when they upgrade sendmail. I will try to track down and replace my usages of /usr/lib/sendmail with /usr/sbin/sendmail, but this doesn't change the fact that you shouldn't break /usr/lib/sendmail on upgrade unless you're consciously choosing not to support it at all anymore.
Fixed in rawhide in rpm sendmail-8.2.11-2 or newer.