lockfile: Improve log message when a process tries to relock a file.

"Resource deadlock avoided" is a pretty obscure message.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Alex Wang <alexw@nicira.com>
ovsdb-server: Improve message for "add-db" of database already open.

Otherwise you get a fairly obscure message about a lockfile already being
locked.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Alex Wang <alexw@nicira.com>