[modular] rename BaseMgr::State::Terminating -> BaseMgr::State::SHUTTING_DOWN

Test=None; no behaviour change.

Change-Id: Ib5b5996f0395e52b15da37cdc3079bc328a552d1
diff --git a/bin/basemgr/basemgr_impl.cc b/bin/basemgr/basemgr_impl.cc
index a564274..af2acec 100644
--- a/bin/basemgr/basemgr_impl.cc
+++ b/bin/basemgr/basemgr_impl.cc
@@ -302,11 +302,11 @@
 
 void BasemgrImpl::Shutdown() {
   // Prevent the shutdown sequence from running twice.
-  if (state_ == State::TERMINATING) {
+  if (state_ == State::SHUTTING_DOWN) {
     return;
   }
 
-  state_ = State::TERMINATING;
+  state_ = State::SHUTTING_DOWN;
 
   FXL_DLOG(INFO) << "fuchsia::modular::BaseShellContext::Shutdown()";
 
diff --git a/bin/basemgr/basemgr_impl.h b/bin/basemgr/basemgr_impl.h
index 734d640..9318b2d 100644
--- a/bin/basemgr/basemgr_impl.h
+++ b/bin/basemgr/basemgr_impl.h
@@ -183,7 +183,7 @@
     // normal mode of operation
     RUNNING,
     // basemgr is shutting down.
-    TERMINATING
+    SHUTTING_DOWN
   };
 
   State state_ = State::RUNNING;