ovs-ctl: Connect to remote OVSDB managers only after ovs-vswitchd starts.

ovs-ctl: Connect to remote OVSDB managers only after ovs-vswitchd starts.

Until now, ovs-ctl has started ovsdb-server with the full set of remote
managers configured.  This means that ovsdb-server immediately connects to
these managers, before ovs-vswitchd even starts.  Because the Open vSwitch
schema has several ephemeral columns, there will be considerable startup
churn in the database.   For example, ovs-vswitchd will initially fill in
the datapath-id and ofport columns as it starts and sets up the initial
configuration.  This churn wastes bandwidth to the remote managers and has
potential for confusing them.

This commit reduces the churn by changing ovs-ctl so that ovsdb-server
connects to the remote managers only after ovs-vswitchd has finished its
initial configuration.  This means that remote managers will initially
see a filled-in database, not one that has its ephemeral columns empty.

This commit does not mean that managers can ignore the possibility that
some columns have not yet been filled in.  For example, some columns will
still be briefly blank after a new bridge or a new port is added at
runtime, because adding a bridge or port occurs in one transaction (made by
the client adding the port, e.g. ovs-vsctl) and filling in those columns
happens in a different transaction (made by ovs-vswitchd).  But this commit
does reduce the quantity of empty columns that I would expect a database
client to observe in practice.

Reported-by: Jeff Merrick <jmerrick@vmware.com>
CC: Amar Padmanabhan <amar@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ansis Atteka <aatteka@nicira.com>
Bug #15983.