Upgrade JGit to 5.3.4.201908231101-r

Improvements in 5.3.4:
- measure FileStoreAttributes per filesystem
  - improve measuring file timestamp resolution
  - measure minimal racy interval
  - use Instant to increase resolution to 1us (limited by FileTime)
  - persist FileStoreAttributes
  - optional asynchronous measurement of FileStoreAttributes
  - directory - FileStore cache
- cache user and system level gitconfig
- fix supportsAtomicCreateNewFile default to true
- fix non-deterministic hash of archives created by ArchiveCommand

Release notes:
https://projects.eclipse.org/projects/technology.jgit/releases/5.3.4

Change-Id: I6771cdccd1d27dd5886d2f75e6c906448e1bed59

java/com/google/gerrit/server/util/time/TimeUtil.java

@@ -15,10 +15,13 @@
 package com.google.gerrit.server.util.time;
 
 import com.google.common.annotations.VisibleForTesting;
+import java.io.IOException;
 import java.sql.Timestamp;
 import java.time.Instant;
 import java.util.function.LongSupplier;
+import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.StoredConfig;
 import org.eclipse.jgit.storage.file.FileBasedConfig;
 import org.eclipse.jgit.util.FS;
 import org.eclipse.jgit.util.SystemReader;
@@ -104,6 +107,16 @@ public class TimeUtil {
     public int getTimezone(long when) {
       return delegate.getTimezone(when);
     }
+
+    @Override
+    public StoredConfig getUserConfig() throws IOException, ConfigInvalidException {
+      return delegate.getUserConfig();
+    }
+
+    @Override
+    public StoredConfig getSystemConfig() throws IOException, ConfigInvalidException {
+      return delegate.getSystemConfig();
+    }
   }
 
   private TimeUtil() {}