fix: don't log query 'select $$'

Looks like it is kind of erroneous query sent by some versions of mysql
cli.

ref: #2772

Author: klirichek

src/daemon/query_log.cpp

@@ -702,6 +702,11 @@ void LogSphinxqlError ( const char * sStmt, const Str_t & sError )
 	if ( g_eLogFormat != LOG_FORMAT::SPHINXQL || g_iQueryLogFile < 0 || !sStmt || IsEmpty ( sError ) )
 		return;
 
+	// some mysql cli, like mysql 9.0.1, 9.1.0, 9.3.0, may be others, fire 'select $$' query after connect
+	// that produces some noise in query log, so let's just filter out these queries. #2772
+	if ( !strcmp (sStmt, "select $$") )
+		return;
+
 	StringBuilder_c tBuf;
 	tBuf << "/* ";
 	FormatTimeConnClient ( tBuf );