test: don't put $BINDIR in $PATH for test-merge-tools.t...
test: don't put $BINDIR in $PATH for test-merge-tools.t
We call $BINDIR/hg explicitly anyway, so don't need it in $PATH. This
fixes failures when running the test --with-hg=/usr/bin/hg, where we
pick up /usr/bin/false as merge tool when we expected not to find it.
