"un-skip" more skipped tests

* version_compile_os can be "linux-systemd", not equal to "Linux"
* main.no-threads forces no-threads scheduler, a check whether it
  has one_thread_per_connection is guaranteed to fail.

mysql-test/include/linux.inc

@@ -1,4 +1,4 @@
-if (`select convert(@@version_compile_os using latin1) LIKE 'Linux' = 0`)
+if (`select @@version_compile_os not LIKE 'Linux%'`)
 {
   skip Need Linux;
 }