Fix get_node_by_path string equality check

When determining if to recurse into a node, get_node_by_path does not
check if the length of each node name is equal.  If searching for
/foo/baz, this can result in recursing into /foobar because
strneq("foo", "foobar", 3) is true.

This can result in a reference to /foo/baz to be incorrectly set to
/foobar/baz.  A test for this was added.

Signed-off-by: Tim Montague <tmontague@ghs.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>