tests: Suppress valgrind FP's caused by Rust std library hack

See:
- https://github.com/fede1024/rust-rdkafka/blob/master/rdkafka.suppressions
- https://sourceware.org/git/?p=valgrind.git;a=commit;h=2a7d3ae768f9e5b29acd5cb743c3fb13640a391c

unit_tests/valgrind.supp

@@ -314,3 +314,21 @@
    fun:recvloop
    fun:main
 }
+{
+   rust_statx_hack-unaddressable_bytes
+   Memcheck:Param
+   statx(file_name)
+   fun:statx
+   fun:statx
+   fun:_ZN3std3sys4unix2fs9try_statx17h3116b93d19baec3cE
+   ...
+}
+{
+   rust_statx_hack-unaddressable_bytes2
+   Memcheck:Param
+   statx(buf)
+   fun:statx
+   fun:statx
+   fun:_ZN3std3sys4unix2fs9try_statx17h3116b93d19baec3cE
+   ...
+}