THRIFT-4582: Fix Xenial CI build issues (#1563)

* THRIFT-4582: fix xenial build issues

* THRIFT-2913: fix Thrift::ThreadPoolServer should serve inside a thread on xenial

* THRIFT-4478: Move Xenial up to dmd 2.075.1 as that is the new minimum
version that works since the changes for 2.080.0 went in.
diff --git a/lib/erl/rebar.test.config b/lib/erl/rebar.test.config
index 12515b7..2ff2afb 100644
--- a/lib/erl/rebar.test.config
+++ b/lib/erl/rebar.test.config
@@ -1,5 +1,5 @@
 {erl_opts, [{platform_define, "^R.*", otp16_or_less}, debug_info]}.
 
 {deps, [
-  {meck, "", {git, "https://github.com/eproxus/meck.git", {tag, "0.8.2"}}}
+  {meck, "", {git, "https://github.com/eproxus/meck.git", {tag, "0.8.9"}}}
 ]}.