[thread-safety] add . to dummy fieldname

Summary:
Otherwise, we can get an exception when calling `Fieldname.java_get_field`.
Thanks to ngorogiannis for reporting.

Reviewed By: jeremydubreil

Differential Revision: D4805197

fbshipit-source-id: 3141bb1

infer/src/checkers/ThreadSafety.ml

@@ -27,7 +27,7 @@ let is_owned access_path attribute_map =
   ThreadSafetyDomain.AttributeMapDomain.has_attribute
     access_path ThreadSafetyDomain.Attribute.unconditionally_owned attribute_map
 
-let container_write_string = "__CONTAINERWRITE__"
+let container_write_string = "infer.dummy.__CONTAINERWRITE__"
 
 let is_container_write_str str =
   String.is_substring ~substring:container_write_string str