Patch developed inhouse and has been accepted by the community.
Details can be found at
https://sourceforge.net/p/net-snmp/bugs/2654/
The community patch differs slightly from this as it needs to be
generic for all OSes, hence they have included an extra check for the availability
of the forkall function. 
--- net-snmp-5.4.1.old/apps/snmptrapd.c	2007-06-08 03:44:37.000000000 -0700
+++ net-snmp-5.4.1/apps/snmptrapd.c	2015-05-20 05:12:11.512063848 -0700
@@ -1237,7 +1237,7 @@
     if (dofork && netsnmp_running) {
         int             fd;
 
-        switch (fork()) {
+        switch (forkall()) {
         case -1:
             fprintf(stderr, "bad fork - %s\n", strerror(errno));
             _exit(1);