Change: break on insufficient memory

Instead of iterating and checking if there is enough memory available it
is breaking on the first occurence. This allows the scheduler to verify
later again.

rust/openvasd/src/scheduling.rs

@@ -182,7 +182,7 @@ where
                 let available_memory = sys.available_memory();
                 if available_memory < min_free_memory {
                     tracing::debug!(%min_free_memory, %available_memory, "insufficient memory to start a scan.");
-                    continue;
+                    break;
                 }
             }
             if let Some(scan_id) = queued.pop() {