Add external/tlsdate to manifest.

Bug: 22373707

default.xml

@@ -288,6 +288,7 @@
   <project path="external/tinycompress" name="platform/external/tinycompress" groups="pdk" />
   <project path="external/tinyxml" name="platform/external/tinyxml" groups="pdk" />
   <project path="external/tinyxml2" name="platform/external/tinyxml2" groups="pdk" />
+  <project path="external/tlsdate" name="platform/external/tlsdate" />
   <project path="external/toybox" name="platform/external/toybox" groups="pdk" />
   <project path="external/tremolo" name="platform/external/tremolo" groups="pdk" />
   <project path="external/v8" name="platform/external/v8" groups="pdk" />