Run most acceptance tests in-memory

This allows the tests to run faster, with lower system overheads.
The new @UseLocalDisk annotation must be added to any test method
that wants the classical init and daemon testing strategy.

A new sshd.requestLog configuration variable is introduced to
permit tests to disable the SSH command log.

Timing for `buck test --all` on my Linux desktop:

  before 3m37.129s
  after  2m18.789s

Change-Id: I18c07ef2d913f6abbb3925b3e7d3df5d28668497
(cherry picked from commit 318bfcae5c)

gerrit-acceptance-tests/BUCK

@@ -12,6 +12,7 @@ java_library(
     '//gerrit-pgm:pgm',
     '//gerrit-reviewdb:server',
     '//gerrit-server:server',
+    '//gerrit-server:testutil',
     '//gerrit-sshd:sshd',
 
     '//lib:args4j',