Don't swallow JSchException "Auth fail" exception

"Auth fail" exception was swallowed during retrying, this leads to
"Session down" exception during clone operation with invalid SSH keys.

Bug: 336795
Change-Id: Id8d9e83b10f4f2a01e0cf89819190bb23a04a2b9
Signed-off-by: Dariusz Luksza <dariusz@luksza.org>