Apache MINA sshd client: respect NumberOfPasswordPrompts

Apache MINA sshd client: respect NumberOfPasswordPrompts

Set the internal property on the session as defined in the ssh config.

Note that NumberOfPasswordPrompts in openssh applies independently to
both user logins in keyboard-interactive authentication _and_ to
passphrases for identity files (encrypted keys). Apache MINA sshd uses
the setting only for keyboard-interactive authentication, but not for
identity file passphrase prompts. For identity files, it asks exactly
once. This has been reported as issue SSHD-850 upstream.[1]

[1] https://issues.apache.org/jira/browse/SSHD-850

Bug: 520927
Change-Id: I390ffe9e1c52b96d3e8e28fd8edbdc73dde9edb4
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>