sinkclient: add the ability to disable shm via libwrap

This allow to generate jamid for dbus usage and client-qt with
libwrap.

Change-Id: Ia23a0cec2efb4347166e0123c662da6c134c2238
GitLab: jami-project#1312

src/media/video/sinkclient.cpp

@@ -278,6 +278,9 @@ SinkClient::start() noexcept
 {
     if (not shm_) {
         try {
+            char* envvar = getenv("JAMI_DISABLE_SHM");
+            if (envvar) // Do not use SHM if set
+                return true;
             shm_ = std::make_shared<ShmHolder>();
             JAMI_DBG("[Sink:%p] Shared memory [%s] created", this, openedName().c_str());
         } catch (const std::runtime_error& e) {
@@ -426,6 +429,7 @@ SinkClient::update(Observable<std::shared_ptr<MediaFrame>>* /*obs*/,
             return;
         }
 #if HAVE_SHM
+        if (shm_)
             shm_->renderFrame(*frame);
 #endif
         if (target_.pull) {