sqlite3: configure the timeout explicitly.

In flush-cache.sh, we have to do this, because the sqlite3 command-line tool
sets it to zero.  Inevitably during parallel testing, it'll end up
contending for a lock, and we really want it to wait a bit.

In state.py, it's not as important since the default is nonzero.  But
python-sqlite3's default of 5 seconds makes me a little too nervous; I can
imagine a disk write waiting for more than 5 seconds sometime.  So let's use
60 instead.

t/flush-cache.sh

@@ -1,6 +1,7 @@
 #!/bin/sh
 #echo "Flushing redo cache..." >&2
 (
+	echo ".timeout 5000"
 	echo "update Files set checked_runid=null;"
 	echo "update Files set changed_runid=changed_runid-1;"
 	#echo "update Files set stamp='dirty' where id in (select distinct target from Deps);"