JGroups ASYM_ENCRYPT causes error during startup: "key server is currently not set"

Issue

When using ASYM_ENCRYPT in the JGroups stack the error below is reported when the second server instance is joining the cluster.

[Server:server-two] 16:33:34,047 INFO  [org.jboss.as] (Controller Boot Thread) JBAS015874: JBoss EAP 6.4.9.GA (AS 7.5.9.Final-redhat-2) started in 13985ms - Started 318 of 383 services (129 services are lazy, passive or on-demand)
[Server:server-one] 16:33:34,707 DEBUG [org.jgroups.protocols.pbcast.GMS] (ServerService Thread Pool -- 68) election results: {}
[Server:server-one] 16:33:35,211 DEBUG [org.jgroups.protocols.pbcast.GMS] (ServerService Thread Pool -- 68) election results: {master:server-two/ejb=1}
[Server:server-one] 16:33:35,211 DEBUG [org.jgroups.protocols.pbcast.GMS] (ServerService Thread Pool -- 68) sending JOIN(master:server-one/ejb) to master:server-two/ejb
*************************************************************************************************************************************
[Server:server-one] 16:33:35,226 ***ERROR*** [org.jgroups.protocols.ASYM_ENCRYPT] (OOB-4,shared=tcpping) master:server-one/ejb: key server is currently not set
*************************************************************************************************************************************
[Server:server-two] 16:33:35,273 DEBUG [org.jgroups.protocols.pbcast.STABLE] (ViewHandler,ejb,master:server-two/ejb) suspending message garbage collection
[Server:server-two] 16:33:35,274 DEBUG [org.jgroups.protocols.pbcast.STABLE] (ViewHandler,ejb,master:server-two/ejb) resume task started, max_suspend_time=33000
[Server:server-two] 16:33:35,277 DEBUG [org.jgroups.protocols.pbcast.NAKACK2] (Incoming-1,shared=tcpping)
[Server:server-two] [master:server-two/ejb setDigest()]
[Server:server-two] existing digest:  master:server-two/ejb: [1 (1)]
[Server:server-two] new digest:       master:server-two/ejb: [0 (0)], master:server-one/ejb: [0 (0)]
[Server:server-two] resulting digest: master:server-two/ejb: [1 (1)], master:server-one/ejb: [0 (0)]
[Server:server-two] 16:33:35,277 DEBUG [org.jgroups.protocols.pbcast.GMS] (Incoming-1,shared=tcpping) master:server-two/ejb: installing view [master:server-two/ejb|1] [master:server-two/ejb, master:server-one/ejb]
[Server:server-two] 16:33:35,278 DEBUG [org.jgroups.protocols.FD_SOCK] (Incoming-1,shared=tcpping) VIEW_CHANGE received: [master:server-two/ejb, master:server-one/ejb]