interconnect: restart in fast mode so the test does not race crash recovery

The test sets shared_preload_libraries and restarts with "gpstop -raiq".  An
immediate shutdown skips the shutdown checkpoint, so the control file is left
in a state other than DB_SHUTDOWNED and the next startup performs crash
recovery: xlogrecovery.c sets InRecovery, xlog.c calls PerformWalRecovery(),
which signals PMSIGNAL_RECOVERY_STARTED, and the postmaster moves to
PM_RECOVERY.  In that state canAcceptConnections() answers CAC_NOTCONSISTENT,
reported as "the database system is not accepting connections" with detail
"Hot standby mode is disabled".  gpstart makes exactly such a connection right
after pg_ctl returns, to read the segment configuration, so gpstop -r exits
CRITICAL and the restart is reported as failed.

The damage does not stop there.  psql gives up at the \c that follows, so
every statement in the file is skipped and the test fails as a whole; the
cleanup at the end of the file never runs; and gpstart never got past starting
the coordinator in admin mode, so the cluster is left with no segments up.
Suites that run after this one in the same job then lose their Gather Motion
nodes and fail as well.

Shut down fast instead.  A fast shutdown writes the shutdown checkpoint, the
control file says DB_SHUTDOWNED, no recovery runs, PM_RECOVERY is never
entered, and CAC_NOTCONSISTENT cannot be returned -- the failure becomes
unreachable rather than merely less likely.  Fast is also what the rest of the
tree already uses: gpstop -raf/-arf appear in dozens of places, and this file
was the only user of -raiq.

Measured on a three-segment demo cluster, dirtying 1.5M coordinator rows
before each restart so that recovery is slow enough to lose the race
reliably: -raiq failed 2/2 with the message above, -rafq passed 3/3 with all
three segments still up afterwards.  pg_controldata confirms the mechanism at
the other end -- "in production" after an immediate shutdown, "shut down"
after a fast one.  The test still passes under pg_regress with the change.

Author: MisterRaindrop

contrib/interconnect/sql/interconnect.sql

@@ -1,6 +1,12 @@
 -- start_ignore
 \! gpconfig -c shared_preload_libraries -v "interconnect"
-\! gpstop -raiq
+-- Restart in fast mode, not immediate: an immediate shutdown skips the
+-- shutdown checkpoint, so the next startup runs crash recovery, and while the
+-- postmaster is in PM_RECOVERY it rejects the connection gpstart makes to read
+-- the segment configuration ("the database system is not accepting
+-- connections").  gpstop -r then fails, psql gives up at the \c below, and the
+-- whole file is skipped with only the coordinator left running.
+\! gpstop -rafq
 \c
 DROP TABLE IF EXISTS test_ic_data;
 CREATE EXTENSION IF NOT EXISTS interconnect;
@@ -83,5 +89,5 @@ DROP EXTENSION interconnect;
 
 -- start_ignore
 \! gpconfig -r shared_preload_libraries
-\! gpstop -raiq
+\! gpstop -rafq
 -- end_ignore