tests: Invoke daemons with --no-chdir so core files appear in test dir.

tests: Invoke daemons with --no-chdir so core files appear in test dir.

The OVS daemons "cd" to / as a normal part of their startup, since this is
traditional for daemons under Unix.  But this also means that, if the
daemons happen to terminate with a core in the unit tests, then the core
file won't be written because / has too-restrictive permissions.  (Unless
you run the unit tests as root, or you've got cores configured to go to a
non-standard location.)

This commit fixes the problem by invoking most daemons with --no-chdir so
that the core files go to a test-specific directory.  I didn't change
invocations of the Python daemons, since Python doesn't normally terminate
with a core.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Kyle Mestery <kmestery@cisco.com>