Default GERRIT_NOTEDB=ON

We plan to remove ReviewDb support from the master branch before the
next release. Supporting ReviewDb is no longer important enough to
qualify as the default.

Change-Id: I558bfeeef804680130a5d9404b347c590543f58c

Documentation/dev-bazel.txt

@@ -258,8 +258,10 @@ To run a specific test group, e.g. the rest-account test group:
   bazel test //javatests/com/google/gerrit/acceptance/rest/account:rest_account
 ----
 
-To run the tests against NoteDb backend with write
-to NoteDb, but not read from it:
+The tests run with NoteDb fully enabled by default.
+
+To run the tests against NoteDb backend with write to NoteDb, but not read from
+it:
 
 ----
   bazel test --test_env=GERRIT_NOTEDB=WRITE //...
@@ -277,10 +279,10 @@ Primary storage NoteDb:
   bazel test --test_env=GERRIT_NOTEDB=PRIMARY //...
 ----
 
-Primary storage NoteDb and ReviewDb disabled:
+NoteDb entirely disabled:
 
 ----
-  bazel test --test_env=GERRIT_NOTEDB=ON //...
+  bazel test --test_env=GERRIT_NOTEDB=OFF //...
 ----
 
 To run only tests that do not use SSH:

Documentation/dev-intellij.txt

@@ -177,9 +177,9 @@ Normally, this approach generates JUnit run configurations. When the Bazel
 plugin manages a project, it intercepts the creation and creates a Bazel test
 run configuration instead, which can be used just like the standard ones.
 
-TIP: If you would like to execute a test in NoteDb mode, add
-`--test_env=GERRIT_NOTEDB=READ_WRITE` to the *Bazel flags* of your run
-configuration.
+TIP: Tests run with NoteDb enabled by default. If you would like to execute a
+test with NoteDb turned off, add `--test_env=GERRIT_NOTEDB=OFF` to the *Bazel
+flags* of your run configuration.
 
 [[remote-debug]]
 === Debugging a remote Gerrit server

java/com/google/gerrit/testing/NoteDbMode.java

@@ -52,7 +52,7 @@ public enum NoteDbMode {
       value = System.getProperty(SYS_PROP);
     }
     if (Strings.isNullOrEmpty(value)) {
-      return OFF;
+      return ON;
     }
     value = value.toUpperCase().replace("-", "_");
     NoteDbMode mode = Enums.getIfPresent(NoteDbMode.class, value).orNull();