Locking fix; spinwait for slice lock in CreateSliver().

It is possible for the CM daemon to grab the lock for a moment,
so lets not fail. Rare case.

protogeni/lib/GeniCMV2.pm.in

@@ -506,7 +506,7 @@ sub CreateSliver($)
     #
     # Leave the slice intact on error, so we can go look at it. 
     #
-    if ($slice->Lock() != 0) {
+    if ($slice->WaitForLock(30) != 0) {
 	print STDERR "CreateSliver: Could not lock $slice before start\n";
 	return GeniResponse->Create(GENIRESPONSE_ERROR, undef,
 				    "Internal Error");

protogeni/lib/GeniSlice.pm.in

@@ -478,6 +478,26 @@ sub UnLock($)
     return 0;
 }
 
+#
+# Wait for lock with timeout (in seconds).
+#
+sub WaitForLock($$)
+{
+    my ($self, $timeout) = @_;
+
+    return $self->Lock()
+	if (! $timeout);
+	
+    while ($timeout >= 0) {
+	return 0
+	    if ($self->Lock() == 0);
+	
+	$timeout--;
+	sleep(1);
+    }
+    return -1;
+}
+
 #
 # The stitching lock is used solely for controlling concurrency related
 # to stitching.