Lower the minimum value for MaxMemInQueues to 64 MB for relays.

For clients, there is no minimum value; in both cases, we warn if
the value seems too low.

Closes ticket 24308.
3 jobs for ticket24308_035 in 11 minutes and 2 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
passed #1322
debian-distcheck

00:06:08

passed #1323
debian-docs

00:08:52

passed #1321
debian-minimal

00:05:15