Create git_http_low_speed_limit / git_http_low_speed_time

Expose 2 new settings to zuul.conf allowing an operator better
control over them.  By default we set the speed limit to 1000 bytes
and speed time to 30 seconds.

Change-Id: I9da80fcfc312cbc12ea11ee7284eaec23adb97c9
Signed-off-by: Paul Belanger <pabelanger@redhat.com>
diff --git a/doc/source/admin/components.rst b/doc/source/admin/components.rst
index 5e7e0e1..464cb60 100644
--- a/doc/source/admin/components.rst
+++ b/doc/source/admin/components.rst
@@ -265,6 +265,22 @@
 
       Directory in which Zuul should clone git repositories.
 
+   .. attr:: git_http_low_speed_limit
+      :default: 1000
+
+      If the HTTP transfer speed is less then git_http_low_speed_limit for
+      longer then git_http_low_speed_time, the transfer is aborted.
+
+      Value in bytes, setting to 0 will disable.
+
+   .. attr:: git_http_low_speed_time
+      :default: 30
+
+      If the HTTP transfer speed is less then git_http_low_speed_limit for
+      longer then git_http_low_speed_time, the transfer is aborted.
+
+      Value in seconds, setting to 0 will disable.
+
    .. attr:: git_user_email
 
       Value to pass to `git config user.email