Fix typo in tests

test/regression.uts

@@ -737,7 +737,7 @@ success = False
 for i in xrange(5):
     try:
         IP(src="8.8.8.8").whois()
-    except socker.error:
+    except socket.error:
         time.sleep(2)
     else:
         success = True
@@ -753,7 +753,7 @@ success = False
 for i in xrange(5):
     try:
         ret = conf.AS_resolver.resolve("8.8.8.8", "8.8.4.4")
-    except socker.error:
+    except socket.error:
         time.sleep(2)
     else:
         success = True