I got tired of seeing this.

config.status: executing libtool commands
/bin/rm: cannot remove `libtoolT': No such file or directory
config.status: executing po-directories commands

While I was at it, there were a couple other unused variables.

* configure.ac (RM, MV, TAR): Drop; nothing in libvirt directly uses
this, and assigning RM interferes with libtool.