Fix ExternalFunctionInfo serialization issue.

Make IResultTypeComputer transient to avoid the serialization issue.
Since this attribute is used only query compliation process, transient
can be safely added.

Change-Id: I3b58dd67f9138b0b19d74ee9d42ae8fb82336c13
Reviewed-on: https://asterix-gerrit.ics.uci.edu/1717
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
BAD: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
index 5e74223..9f3b529 100644
--- a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
+++ b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
@@ -28,7 +28,7 @@
 
     private static final long serialVersionUID = 1L;
 
-    private final IResultTypeComputer rtc;
+    private final transient IResultTypeComputer rtc;
     private final List<IAType> argumentTypes;
     private final String body;
     private final String language;