I just encountered this same issue and was able to resolve it by copying the contents of /etc/vmware-eam/eam.properties from a 6.0U3 appliance in my lab. I was then able to start the vmware-eam service and proceed with my 6.5 upgrade.

Below are the contents of the file I used. Maybe it will help someone else who doesn't have a spare appliance sitting around. Note that you need to change the the line vc.tunnelSdkUri=https://vcenter:8089/sdk/vimService to match your hostname.

#########################################################################
# Copyright 2013-2017 VMware, Inc.  All rights reserved. VMware Confidential
#########################################################################
vc.proxy.host=localhost
vc.proxy.port=80
# Hostname or IP of the EAM server
# Fill only if EAM is not running on the same host as VC
eam.host=
# EAM service port used to configure the HTTP connector of the application server.
eam.int.http.port=15005
# Port and scheme configuration which is used by the ESX 6.x hosts to reach EAM Vib
# file server.
eam.ext.port=443
eam.ext.scheme=https
# Port and scheme configuration which is used by the ESX 5.x hosts to reach EAM Vib
# file server.
eam.ext.port.deprecated=80
eam.ext.scheme.deprecated=http
eam.support_linked_clone=true
eam.clear_db_on_startup=false
eam.debug_ref_count=false
eam.recent_event_size=20
# Value is specified in minutes (set to 24h = 1440m)
eam.scan_for_unknown_agent_vms=1440
# The timeout to wait for hostd to restart on a host (set to 5m=300s)
eam.hostd_restart_timeout=300
# The following entries will be added verbatim to the advanced options
# of hosts on which EAM is enabled. All are optional.
Net.DVFilterBindIpAddress=169.254.0.1
Net.TrafficFilterIpAddress=
#The IP for the VSWIF NIC on the dvFilter switch (for ESX classic).
Net.DVFilterVswifIpAddress=169.254.0.2
# Resource bundle configuration
eam.resourcebundle.filename=eam-resourcebundle.jar
# VLSI embedded tcServer configuration
#
tcserver.tmp.dir=/var/tmp/vmware/eam/tomcat
eam.web.root=/usr/lib/vmware-eam/web
# EAM SSL configuration
#
eam.keystore.type=VKS
eam.key.alias=vpxd-extension
eam.keystore.storename=vpxd-extension
# CM configuration
#
cm.url=http://localhost:18090/cm/sdk/?hostid=fa3bd34a-4b3c-4ff0-ad4f-1c97ad6f93b5
cm.wait.attempts=360
cm.wait.intervalSeconds=5
# SSO configuration
#
sso.wait.attempts=360
sso.wait.intervalSeconds=5
# VC SSL configuration
#
vc.truststore.type=VKS
vc.truststore.storename=TRUSTED_ROOTS
vc.tunnelSdkUri.template=https://##{VC_HOST_NAME}##:8089/sdk/vimService
vc.tunnelSdkUri=https://vcenter:8089/sdk/vimService
drs.demandCapacityRatio=100