Reduce default maximum connection timeout from 15 seconds to 8 seconds.

Reduce default maximum connection timeout from 15 seconds to 8 seconds.

Users at Nicira have commented that a maximum reconnection time of 15
seconds, which was the default, is too long.  This commit cuts it to 8
seconds, on the theory that an administrator is willing to wait that long
before deciding that a change that should restore connectivity did not
work.