Test the return value of QEventLoop::exec earlier.

The clang-tidy "implicit boolean conversion" check pointed out a
function where an integer was implicitly converted to a boolean and
then later implicitly converted back to an integer for an 'if'
statement.  Fix both of these implicit conversions.

https://clang.llvm.org/extra/clang-tidy/checks/readability-implicit-bool-conversion.html

mythtv/libs/libmythbase/mythsingledownload.cpp

@@ -37,13 +37,13 @@ bool MythSingleDownload::DownloadURL(const QUrl &url, QByteArray *buffer,
     m_timer.setSingleShot(true);
     m_timer.start(timeout);  // 30 secs. by default
 
-    bool ret = event_loop.exec(); // blocks stack until quit() is called
+    bool ret = event_loop.exec() != 0; // blocks stack until quit() is called
 
     disconnect(&m_timer, SIGNAL(timeout()), &event_loop, SLOT(quit()));
     disconnect(m_reply, SIGNAL(finished()), &event_loop, SLOT(quit()));
     disconnect(m_reply, SIGNAL(downloadProgress(qint64,qint64)), this, SLOT(Progress(qint64,qint64)));
 
-    if (ret != 0)
+    if (ret)
     {
         LOG(VB_GENERAL, LOG_ERR, LOC + "evenloop failed");
     }