Update target platforms, maven and bazel builds to use sshd 2.2.0.
Adapt internal classes to changed sshd interfaces and remove previous
work-arounds for asking repeatedly for key passwords and for loading
keys lazily; both are now done by sshd.
CQ: 19034
CQ: 19035
Bug: 541425
Change-Id: I85e1df6ebb8a94953a912d9b2b8a7b5bdfbd608a
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>