Fix up "make check"

Fix up "make check"

While running make check, I noticed that it was actually using
the virsh binary from my system, in /usr/bin/virsh, and not the
one that was just compiled.  This is actually caused by a bug
in Makefile.am, where we didn't update the PATH to include tools.

While here, I also updated all of the scripts to properly define
the srcdir, abs_top_srcdir, and abs_top_builddir environment
variables.  This is required if you want to be able to run the
tests standalone (i.e. ./test instead of from make check).  I've
tested this on both RHEL-5 and Fedora-10 machines, and make check
works on both, as does running the individual tests by hand.

Signed-off-by: Chris Lalancette <clalance@redhat.com>