Set crosvm as the default VMM for cuttlefish

Test: TH, Forrest, GCE and locally
Bug: 127361363
Change-Id: I7f9a019771da7d0f9ee835a85de6b09e85bfb5d7
diff --git a/host/commands/launch/flags.cc b/host/commands/launch/flags.cc
index 510d235..f7f5d63 100644
--- a/host/commands/launch/flags.cc
+++ b/host/commands/launch/flags.cc
@@ -85,7 +85,7 @@
 DEFINE_string(instance_dir, "", // default handled on ParseCommandLine
               "A directory to put all instance specific files");
 DEFINE_string(
-    vm_manager, vm_manager::QemuManager::name(),
+    vm_manager, vm_manager::CrosvmManager::name(),
     "What virtual machine manager to use, one of {qemu_cli, crosvm}");
 DEFINE_string(
     gpu_mode, vsoc::kGpuModeGuestAshmem,