ovsdb-server: Preserve remotes across crash and restart.

ovsdb-server: Preserve remotes across crash and restart.

Commit b421d2af0ab (ovsdb-server: Add commands for adding and removing
remotes) made it possible to make ovsdb-server connect to OVS managers only
after ovs-vswitchd has completed its initial configuration.  But this
results in an undesirable effect: whenever ovsdb-server crashes, the
monitor restarts its, but ovsdb-server can no longer connect to the manager
because the remotes were added during runtime and that information is lost
during the crash.

This commit fixes the problem.

Signed-off-by: Ben Pfaff <blp@nicira.com>