job-manager: add alloc_acct_fudge_free()

Problem: the housekeeping subsystem will need a way to adjust
R accounting when handling RFC 27 hello responses, since partial
release is not yet supported.

Add alloc_acct_fudge_free() for that purpose, and make acct_free()
able to handle a NULL R now that it no longer purely an internal
function.

src/modules/job-manager/alloc.c

@@ -121,6 +121,10 @@ static int acct_free (struct alloc *alloc, json_t *R, flux_error_t *error)
 
     acct_restart (alloc);
 
+    if (!R) {
+        errprintf (error, "resource accounting error (free): R is NULL");
+        goto done;
+    }
     if (!(rl = rlist_from_json (R, NULL))) {
         errprintf (error, "resource accounting error (free): %s", jerror.text);
         goto done;
@@ -137,6 +141,13 @@ static int acct_free (struct alloc *alloc, json_t *R, flux_error_t *error)
     return rc;
 }
 
+void alloc_acct_fudge_free (struct alloc *alloc, json_t *R, const char *who)
+{
+    flux_error_t error;
+    if (acct_free (alloc, R, &error) < 0)
+        flux_log (alloc->ctx->h, LOG_ERR, "%s: %s", who, error.text);
+}
+
 static void requeue_pending (struct alloc *alloc, struct job *job)
 {
     struct job_manager *ctx = alloc->ctx;

src/modules/job-manager/alloc.h

@@ -75,6 +75,11 @@ void alloc_disconnect_rpc (flux_t *h,
 
 bool alloc_sched_ready (struct alloc *alloc);
 
+/* Hook for marking resources free without going through normal channels.
+ * N.B. Required for RFC 27 workaround in housekeeping_hello_respond().
+ */
+void alloc_acct_fudge_free (struct alloc *alloc, json_t *R, const char *who);
+
 #endif /* ! _FLUX_JOB_MANAGER_ALLOC_H */
 
 /*