6626677: Error: Unimplemented()/HPI sysMonitorExit is broken on linux

Summary: Remove the definition of NEED_DL_LOCK on platforms with GLIBC
Reviewed-by: dholmes, psoper

src/solaris/hpi/src/linker_md.c

@@ -50,15 +50,6 @@
  */
 sys_mon_t _dl_lock;
 
-/*
- * glibc-2.0 libdl is not MT safe.  If you are building with any glibc,
- * chances are you might want to run the generated bits against glibc-2.0
- * libdl.so, so always use locking for any version of glibc.
- */
-#ifdef __GLIBC__
-    #define NEED_DL_LOCK
-#endif
-
 /*
  * Solaris green threads needs to lock around libdl.so.
  */