I believe that any OH 2.2.0 Snapshot Build above 1009 will not modify the behavior of the SSHd
S1009 upgraded the Karaf version from 4.0.8 to 4.1.2.
The SSHd is a part of the Karaf shell component and doesn’t get refreshed with the openHAB 2.2 Snapshots.
To get a newer version of the SSHd than the current 1.6.0, you would need to get a newer Karaf bundle upgrade from a future OH 2.2 snapshot release.
(or… you could try to manually deploy a newer version of the SSHd bundle 
)
Another thing to try is:
/etc/openhab2/services/runtime.cfg
org.apache.karaf.shell:sshIdleTimeout = 0
Usually, stuff in the /var/lib/openhab2/etc/ folder get created from parameters that you set in the files contained in the /etc/openhab2/ folders
Since sshIdleTimeout = 1800000 is the default (30 mins)… even if you change this setting in the /var/lib/openhab2/etc/org.apache.karaf.shell.cfg file, the setting will most likely be overwritten with the default value after service restart.
Setting the time out in the /etc/openhab2/ area will make OH2 read that parameter and update both the running config as well as the /var/lib/ files.
openhab> config:list |grep sshIdleTimeout
sshIdleTimeout = 0