compsvc: Notify VS when we're ready

Once our server socket is listening, notify virtualizationservice that
we're ready.

Modify clients to wait for ready instead of sleeping.

Bug: 186126194
Test: Manually run compos_key_cmd, compos_verify_key
Change-Id: Ibaff4bf22de9de2aa4faff9e81b24c779643b78c
diff --git a/compos/Android.bp b/compos/Android.bp
index f77b2ca..2597c1c 100644
--- a/compos/Android.bp
+++ b/compos/Android.bp
@@ -34,6 +34,7 @@
     rustlibs: [
         "android.hardware.security.keymint-V1-rust",
         "android.system.keystore2-V1-rust",
+        "android.system.virtualmachineservice-rust",
         "authfs_aidl_interface-rust",
         "compos_aidl_interface-rust",
         "libandroid_logger",
@@ -46,6 +47,7 @@
         "liblibc",
         "liblog_rust",
         "libminijail_rust",
+        "libnix",
         "libring",
         "libscopeguard",
     ],