standalone: Set very long SQLite3 busy timeout in Perl

standalone: Set very long SQLite3 busy timeout in Perl

Without this, big standalone-generate-dump-flight-runvars jobs may
trying to serialise so much work that SQLite3 times out.  And we are
about to introduce an optimisation which makes this much more likely.

In standalone mode we probably don't care much about this timeout at
all.  (It might even be that the user is using sqlite(3) and has
effectively locked the database interactively for an extended period.)

We would prefer to rely on the user to stop anything that seems to
have become stuck.  So set the timeout to 10ks.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>