Decrement context ref count as a last action in program destructor.

- There are various calls to device inside destructor.
- Memory manager is protected via device , which is protected by context.
- If context is destroyed it means that device may be destroyed, which means
that memory manager may be destroyed and we have a seg fault.

Change-Id: I2cb6a69790f53bf2c9fba89160078b009e105574

runtime/program/program.cpp

@@ -98,9 +98,6 @@ Program::Program(Context *context, bool isBuiltIn) : context(context), isBuiltIn
 }
 
 Program::~Program() {
-    if (context && !isBuiltIn) {
-        context->decRefInternal();
-    }
     delete[] genBinary;
     genBinary = nullptr;
 
@@ -129,6 +126,9 @@ Program::~Program() {
         pDevice->getMemoryManager()->checkGpuUsageAndDestroyGraphicsAllocations(globalSurface);
         globalSurface = nullptr;
     }
+    if (context && !isBuiltIn) {
+        context->decRefInternal();
+    }
 }
 
 cl_int Program::createProgramFromBinary(