tests: Make ovsdb-server add/remove remote test faster and more reliable.

tests: Make ovsdb-server add/remove remote test faster and more reliable.

Until now, the "ovsdb-server/add-remote and remove-remote with --monitor"
test killed ovsdb-server with SIGSEGV twice.  Each time, the "--monitor"
option caused the supervisor process to restart the child, but the second
time it incurred a 10-second delay intended to prevent the daemon from
wasting CPU time by restarting itself and dying again very quickly in a
loop.  This made the test take over 10 seconds to execute.  It also made
it occasionally fail because the OVS_WAIT_UNTIL check waits at most
approximately 10 seconds before it decides that the condition that it is
testing for will never occur.

This commit fixes the problem by breaking the test into two tests, each of
which kills ovsdb-server with SIGSEGV only once.

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