Upgrade fails between v5010 and v5030 on the developer portal in a cluster

Symptom

Upgrading the developer portal from v5010 to v5030 is failing on clustered
servers.

The upgrade commands that were run with just the -a parameter i.e.:
>bash 5.0.3.0-APIConnect-Portal-20160803-0132.bin -a

will complete successfully however the command on the final server which
is run with both -a and -i will fail:

>bash 5.0.3.0-APIConnect-Portal-20160803-0132.bin -a -i

The file /var/log/syslog on this server will show the error message:

Aug 30 10:31:19 devportal3 mysqld: 160830 10:31:19 [ERROR] WSREP: failed to open gcomm backend connection: 110: failed to reach primary view: 110 (Connection timed out)
Aug 30 10:31:19 devportal3 mysqld: #011 at gcomm/src/pc.cpp:connect():162
Aug 30 10:31:19 devportal3 mysqld: 160830 10:31:19 [ERROR] WSREP: gcs/src/gcs_core.cpp:gcs_core_open():208: Failed to open backend connection: -110 (Connection timed out)
Aug 30 10:31:19 devportal3 mysqld: 160830 10:31:19 [ERROR] WSREP: gcs/src/gcs.cpp:gcs_open():1380: Failed to open channel 'Devportal Cluster' at 'gcomm://devportal1,devportal2,devportal3': -110 (Connection timed out)
Aug 30 10:31:19 devportal3 mysqld: 160830 10:31:19 [ERROR] WSREP: gcs connect failed: Connection timed out
Aug 30 10:31:19 devportal3 mysqld: 160830 10:31:19 [ERROR] WSREP: wsrep::connect(gcomm://devportal1,devportal2,devportal3) failed: 7
Aug 30 10:31:19 devportal3 mysqld: 160830 10:31:19 [ERROR] Aborting

Checking the file /var/log/syslog on one of the other nodes will show error
messages like:
[ERROR] WSREP: handshake with remote endpoint ssl://devportal3:4567  
failed: 1: 'SSL error.' ( 336031996: 'error:140770FC:SSL                
routines:SSL23_GET_SERVER_HELLO:unknown protocol')