CCDB: Ensure CCDBDownloader's libuv loop is properly deleted (AliceO2…

…Group#13238)

My valgrind checks were showing that the internal CCDBDownloader's libuv loop resources were not fully released. With this fix, valgrind is happy.

The change is based on the following premises:
- `uv_loop_alive` returns true if there are *active* handles
- `uv_loop_close` returns `UV_EBUSY` if there are *open* handles.
- we need to succesfully call `uv_loop_close` to clear `mUVLoop` resources

Thus, in case that we would not have *active* handles, we would never close *open* ones, and consequently would not manage to call `uv_loop_close` without getting `UV_EBUSY`.

CCDB/src/CCDBDownloader.cxx

@@ -114,7 +114,7 @@ CCDBDownloader::~CCDBDownloader()
 
   if (!mExternalLoop) {
     // Schedule all handles to close. Execute loop to allow them to execute their destructors.
-    while (uv_loop_alive(mUVLoop) && uv_loop_close(mUVLoop) == UV_EBUSY) {
+    while (uv_loop_alive(mUVLoop) || (uv_loop_close(mUVLoop) == UV_EBUSY)) {
       uv_walk(mUVLoop, closeHandles, this);
       uv_run(mUVLoop, UV_RUN_ONCE);
     }