Move the maxSessionAge init for SystemConfig to GerritServer

This is where the rest of the system configuration is stored,
so we should initialize it there, to reduce confusion about
how the default setup is obtained.

Signed-off-by: Shawn O. Pearce <sop@google.com>

appjar/src/main/java/com/google/gerrit/client/reviewdb/SystemConfig.java

@@ -55,10 +55,10 @@ public final class SystemConfig {
     HTTP;
   }
 
+  /** Construct a new, unconfigured instance. */
   public static SystemConfig create() {
     final SystemConfig r = new SystemConfig();
     r.singleton = new SystemConfig.Key();
-    r.maxSessionAge = 12 * 60 * 60 /* seconds */;
     return r;
   }
 

appjar/src/main/java/com/google/gerrit/server/GerritServer.java

@@ -211,6 +211,7 @@ public class GerritServer {
     c.accountGroups().insert(Collections.singleton(registered));
 
     final SystemConfig s = SystemConfig.create();
+    s.maxSessionAge = 12 * 60 * 60 /* seconds */;
     s.xsrfPrivateKey = SignedToken.generateRandomKey();
     s.accountPrivateKey = SignedToken.generateRandomKey();
     s.sshdPort = 29418;