dbus: install the bus policy in $datadir/dbus-1/system.d

make distcheck fails in install:

    /usr/bin/install: cannot create regular file '/etc/dbus-1/system.d/org.finit.conf': Permission denied

The policy was installed to $sysconfdir/dbus-1/system.d.  distcheck only
overrides the prefix, so the file escaped its sandbox and aimed for the
real /etc.

Install it where dbus looks for package owned policy, leaving
/etc/dbus-1/system.d to the admin.  The test bus config reads it
relative to itself.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

dbus-1/Makefile.am

@@ -1,6 +1,6 @@
 EXTRA_DIST          = org.finit.conf
 
 if DBUS
-dbuspolicydir       = $(sysconfdir)/dbus-1/system.d
+dbuspolicydir       = $(datadir)/dbus-1/system.d
 dist_dbuspolicy_DATA = org.finit.conf
 endif