conf: route service conditions through one owner primitive

A service's condition was computed with mkcond() at each of the six
sites that assert or clear it, and svc_find_by_cond() reimplemented
the reverse lookup a seventh time.  maybe_clear_cond() had its own
scan for another service supplying the same condition.

svc_cond_owner() answers who owns a condition, svc_cond_nth() walks
the conditions a service owns, and svc_cond_set()/svc_cond_clear()
apply to all of them.  svc_find_by_cond() becomes a wrapper, and
maybe_clear_cond() keeps its rule per condition rather than for the
one it used to compute.

The provides[] storage lands here unused, since svc_cond_nth() reads
num_provides.  Nothing sets it yet, so a service still owns exactly
its own pid/<ident> and there is no functional change.

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

src/cond-w.c

@@ -145,6 +145,31 @@ char *mkcond(svc_t *svc, char *buf, size_t len)
 	return buf;
 }
 
+/*
+ * Assert or clear every condition a service owns: its own pid/<ident>
+ * and anything it declares with provides.  Each site that owns a
+ * service's conditions goes through these, so the two cannot drift.
+ */
+void svc_cond_set(svc_t *svc)
+{
+	char buf[MAX_COND_LEN];
+	const char *cond;
+	int i = 0;
+
+	while ((cond = svc_cond_nth(svc, i++, buf, sizeof(buf))))
+		cond_set(cond);
+}
+
+void svc_cond_clear(svc_t *svc)
+{
+	char buf[MAX_COND_LEN];
+	const char *cond;
+	int i = 0;
+
+	while ((cond = svc_cond_nth(svc, i++, buf, sizeof(buf))))
+		cond_clear(cond);
+}
+
 static int cond_set_gen(const char *file, unsigned int gen)
 {
 	char *ptr, path[256];