COMPMID-1478: Stop relying on static default OpenCL objects in cl2.hpp

This causes problems when ACL is used as a shared library on Android.
Fixes some problems related to creation / destruction order between the Graph's CL backend and core / runtime

Change-Id: I716d63fd42f4586df1ffbb6fa97e4db06d3a781b
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/143228
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele DiGiorgio <michele.digiorgio@arm.com>
Reviewed-by: Gian Marco Iodice <gianmarco.iodice@arm.com>
diff --git a/src/graph/frontend/Stream.cpp b/src/graph/frontend/Stream.cpp
index 96a166c..878d688 100644
--- a/src/graph/frontend/Stream.cpp
+++ b/src/graph/frontend/Stream.cpp
@@ -33,7 +33,7 @@
 namespace frontend
 {
 Stream::Stream(size_t id, std::string name)
-    : _manager(), _ctx(), _g(id, std::move(name))
+    : _ctx(), _manager(), _g(id, std::move(name))
 {
 }
 
@@ -66,4 +66,4 @@
 }
 } // namespace frontend
 } // namespace graph
-} // namespace arm_compute
\ No newline at end of file
+} // namespace arm_compute