Fixed bug with download url

The devserver url was giving back inconsistent paths for files.
This has been changed on the devsever side to always be
case sensitive. This change is to reflect that.

BUG=b:36257342
TEST=None

Change-Id: I6aac21f60c9c55d1a555e4134a8485d77c90cdc9
Reviewed-on: https://chromium-review.googlesource.com/455984
Tested-by: Benjamin Peake <bpeake@chromium.org>
Reviewed-by: Dan Shi <dshi@google.com>
Reviewed-by: Joe Brennan <jmbrenna@google.com>
Commit-Queue: Benjamin Peake <bpeake@chromium.org>
diff --git a/server/hosts/adb_host.py b/server/hosts/adb_host.py
index 5eff56d..210774b 100644
--- a/server/hosts/adb_host.py
+++ b/server/hosts/adb_host.py
@@ -1307,9 +1307,8 @@
         """
         # Append the file name to the url if build_url is linked to the folder
         # containing the file.
-        build_url = build_url.lower()
-        if not build_url.endswith('/%s' % file.lower()):
-            src_url = os.path.join(build_url, file.lower())
+        if not build_url.endswith('/%s' % file):
+            src_url = os.path.join(build_url, file)
         else:
             src_url = build_url
         dest_file = os.path.join(dest_dir, file)