Hi !
the SRX answer tells you that on the secondary node there is no routing active.
In order to reach any remote network address with the SSH return packet you need to define a gateway address
put under the group: node0 and node 1
set system backup-router<Ip-gateway-address>
does exactly that
see page 11 of
http://kb.juniper.net/library/CUSTOMERSERVICE/GLOBAL_JTAC/SRX-cluster-monitoring-best-practices.pdf
regards
alexander