Rename some build rules to meet expectation in JGit bazel build

This is a preparation to link JGit as a submodule instead of an
external Maven build dependency.

Change-Id: Icd470c32b6b0447b480bc494ea5ebf558c24e34c

BUILD

diff --git a/BUILD b/BUILD
index d65fe65..3d84a08 100644
--- a/BUILD
+++ b/BUILD
@@ -6,7 +6,7 @@
     libs = [
         "//lib/jetty:server",
         "//lib/jetty:servlet",
-        "//lib/slf4j:slf4j-simple",
+        "//lib:slf4j-simple",
         "//java/com/google/gitiles:servlet",
     ],
     web_xml = "//resources:web_xml",