Similar to git config file reading lock the file only when writing.
There may still be lock conflicts on writing, but those in the worst
case result in an entry not being added and thus being asked for later
again.
Because the OpenSshServerkeyDatabase and its HostKeyFiles may be (and
usually are) shared between different SSH sessions, we still need to
ensure in-process mutual exclusion.
Bug: 559548
Change-Id: I4af97628deff9eaac2520576917c856949f2680d
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
2345cc88d0