mlock: fail gracefully if libc.so.6 cannot be loaded

This allows noded to continue instead of blowing up if the libc major
number changes.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

lib/utils/mlock.py

@@ -51,7 +51,11 @@ def Mlockall(_ctypes=ctypes):
   if _ctypes is None:
     raise errors.NoCtypesError()
 
-  libc = _ctypes.cdll.LoadLibrary("libc.so.6")
+  try:
+    libc = _ctypes.cdll.LoadLibrary("libc.so.6")
+  except EnvironmentError, err:
+    logging.error("Failure trying to load libc: %s", err)
+    libc = None
   if libc is None:
     logging.error("Cannot set memory lock, ctypes cannot load libc")
     return