Parametrized lock test and make it work with MPI

- Lock test can be run either as a node-local test or as an MPI test.

- Lock test is now parametrized by filesystem, so you can test the
  locking capabilities of your NFS, Lustre, or GPFS filesystem.  See docs
  for details.

lib/spack/llnl/util/lock.py

@@ -127,8 +127,9 @@ def _lock(self, op, timeout=_default_timeout):
 
                 return
 
-            except IOError as error:
-                if error.errno == errno.EAGAIN or error.errno == errno.EACCES:
+            except IOError as e:
+                if e.errno in (errno.EAGAIN, errno.EACCES):
+                    # EAGAIN and EACCES == locked by another process
                     pass
                 else:
                     raise
@@ -197,6 +198,8 @@ def acquire_read(self, timeout=_default_timeout):
             tty.debug('READ LOCK: {0.path}[{0._start}:{0._length}] [Acquiring]'
                       .format(self))
             self._lock(fcntl.LOCK_SH, timeout=timeout)   # can raise LockError.
+            tty.debug('READ LOCK: {0.path}[{0._start}:{0._length}] [Acquired]'
+                      .format(self))
             self._reads += 1
             return True
         else:
@@ -219,6 +222,8 @@ def acquire_write(self, timeout=_default_timeout):
                 'WRITE LOCK: {0.path}[{0._start}:{0._length}] [Acquiring]'
                 .format(self))
             self._lock(fcntl.LOCK_EX, timeout=timeout)   # can raise LockError.
+            tty.debug('WRITE LOCK: {0.path}[{0._start}:{0._length}] [Acquired]'
+                      .format(self))
             self._writes += 1
             return True
         else: