vlnsystems,
The CSR1000V in the Amazon Cloud is a fully functional version of the CSR1000V running 3.11 software. As such it supports all features that the CSR1000V supports including the following VPN features:
IPSEC VPNs
-DMVPN
-EasyVPN
-FlexVPN
Here is a link for the configuration guide for IOS-XE EasyVPN configuration:
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_conn_esyvpn/configuration/xe-3s/sec-easy-vpn-xe-3s-book/sec-easy-vpn-srvr.html#GUID-E3CA95DA-1F9A-41B3-A6E6-B4D442162246
As well as some additional information about the CSR1000V:
Q&A for the CSR1000V
CSR1000V DataSheet
So assuming that the Ubunt vpnc client is connecting to your ASA with EasyVPN there should be no problem also connecting to a CSR1000V in the Amazon cloud.
-Nick