sysroot: Prep refactoring of cleanup logic

For future work I'm going to tweak how we handle cleanup, and
the private cleanup flags didn't really end up being used - we
only specify "prune repo or not".  So fold that into a boolean for now.

The sysroot deploy logic then has a single "do_postclean" boolean, which is all
I want to expose as public API.

Closes: #744
Approved by: jlebon

src/libostree/ostree-sysroot.c

@@ -1604,8 +1604,7 @@ ostree_sysroot_simple_write_deployment (OstreeSysroot      *sysroot,
     }
 
   if (!_ostree_sysroot_write_deployments_internal (sysroot, new_deployments,
-                                                   postclean ? OSTREE_SYSROOT_CLEANUP_ALL : 0,
-                                                   cancellable, error))
+                                                   postclean, cancellable, error))
     goto out;
 
   ret = TRUE;