ndbreopen does not close the old file
descriptor.

Reference: /n/patches.lsub.org/patch/ndbreopen.1
Date: Fri Jun 29 18:49:51 CES 2012
Signed-off-by: esoriano@lsub.org

--- /sys/src/libndb/ndbopen.c	Thu Apr 12 12:26:24 2012
+++ /sys/src/libndb/ndbopen.c	Fri Jun 29 18:23:21 2012
@@ -70,6 +70,7 @@
 	if(db == 0)
 		return 0;
 	memset(db, 0, sizeof(Ndb));
+	db->b.fid = -1;
 	strncpy(db->file, file, sizeof(db->file)-1);
 
 	if(ndbreopen(db) < 0){
@@ -89,11 +90,13 @@
 	int fd;
 	Dir *d;
 
+	if(Bfildes(&db->b) >= 0)
+		close(Bfildes(&db->b));
+
 	/* forget what we know about the open files */
 	if(db->mtime){
 		_ndbcacheflush(db);
 		hffree(db);
-		close(Bfildes(&db->b));
 		Bterm(&db->b);
 		db->mtime = 0;
 	}