Upgrade JGit to 0.4.0-212-g9057f1b

This version fixes a race condition in the buffer cache used to
access repository data and thereby fixes some exceptions thrown
while under high concurrent load from clients doing "git clone"
through Gerrit's SSH daemon.

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/pom.xml b/pom.xml
index 798a9f4..1603a76 100644
--- a/pom.xml
+++ b/pom.xml
@@ -500,7 +500,7 @@
     <dependency>
       <groupId>org.spearce</groupId>
       <artifactId>jgit</artifactId>
-      <version>0.4.0-209-g9c26a41</version>
+      <version>0.4.0-212-g9057f1b</version>
       <scope>compile</scope>
     </dependency>