Avoid concurrent access to the datorhandbok server.

check_datorhandbok

@@ -3,6 +3,7 @@
 
 import re
 import urllib2
+import fcntl
 
 import BeautifulSoup
 
@@ -58,7 +59,16 @@ def check_host(hostname):
 
     ok(hostname, "all ok")
 
+def check_host_locked(hostname):
+    f = open("/tmp/datorhandok.lck", "a")
+    try:
+        fcntl.flock(f, fcntl.LOCK_EX)
+        check_host(hostname)
+    finally:
+        fcntl.flock(f, fcntl.LOCK_UN)
+        f.close()
+
 if __name__ == '__main__':
     import sys
 
-    check_host(sys.argv[1])
+    check_host_locked(sys.argv[1])