Commit 7f193757 renamed libvirt-guests.init from .in to .sh, which
made it slip past sc_TAB_in_indentation.  I nearly reintroduced a
tab, so I'm pushing this to prevent that from happening.

* cfg.mk (sc_TAB_in_indentation): Update rule to include .sh files.
* .dir-locals.el: List spacing preference for .sh files.