Bug#28366648 MTR FOR MYSQL5.5 DOES NOT WORK WITH MODERN PERL VERSIONS

Problem: Can't locate lib/mtr_process.pl in @INC

The fix is to push current directory to @INC.

mysql-test/mysql-test-run.pl

@@ -100,6 +100,8 @@ use mtr_results;
 use IO::Socket::INET;
 use IO::Select;
 
+push @INC, ".";
+
 require "lib/mtr_process.pl";
 require "lib/mtr_io.pl";
 require "lib/mtr_gcov.pl";