a56f8b0 Add missing lock in CScheduler::AreThreadsServicingQueue() (Matt Corallo)
Pull request description:
Not an actual bug as this is only used in asserts right now, but nice to not have a missing lock.
Tree-SHA512: 7e542b150a0be716783e196493d239f2ad15e5376abf54b67d735dc3ef1b10849c090337b849f530c9f7497ddcfb8389b47d64a5dcf6382b7d38838f88cc1100
Backport of Core PR 10914
https://github.com/bitcoin/bitcoin/pull/10914/files