tests: virsh is no longer in builddir/src

Commit 870dba07 (Mar 2008) added builddir/src to PATH to pick
up virsh.  Later, virsh was moved to tools; commit db68d6b1
(Oct 2009) noticed this, but only added the new location rather
than deleting the old location.

* tests/Makefile.am (path_add): Drop now-useless directory.
Suggested by Daniel P. Berrange.

tests/Makefile.am

@@ -214,7 +214,7 @@ TESTS += interfacexml2xmltest
 
 TESTS += cputest
 
-path_add = $$abs_top_builddir/src$(PATH_SEPARATOR)$$abs_top_builddir/daemon$(PATH_SEPARATOR)$$abs_top_builddir/tools
+path_add = $$abs_top_builddir/daemon$(PATH_SEPARATOR)$$abs_top_builddir/tools
 
 # NB, automake < 1.10 does not provide the real
 # abs_top_{src/build}dir or builddir variables, so don't rely