autoupdate: remove potential trailing slash from mirror URL

admin/autoupdater/files/usr/sbin/autoupdater

@@ -126,6 +126,9 @@ local function read_manifest(mirror)
 
   local ret = {}
 
+  -- Remove potential trailing slash
+  mirror = mirror:gsub('/$', '')
+
   -- Read all lines from the manifest
   -- The upper part is saves to lines, the lower part to sigs
   for line in io.popen(string.format("exec wget -T 120 -O- '%s/%s.manifest'", mirror, branch.name), 'r'):lines() do