Use AServiceManager_waitForService() to connect to keystore2

Vold currently uses AServiceManager_getService() to connect to
keystore2, which has an internal timeout of 5s. Since a lot of vold
keystore2 connection failures are fatal, we instead use
AServiceManager_waitForService(), which will wait efficiently for
keystore2 to start, instead of timing out after 5s.

Bug: 185934601
Test: Cuttlefish boots.
Change-Id: Ib4e977a997e020082382e0686f448d1aa72834ec
diff --git a/Keymaster.cpp b/Keymaster.cpp
index 1d69dde..8038681 100644
--- a/Keymaster.cpp
+++ b/Keymaster.cpp
@@ -104,7 +104,7 @@
 }
 
 Keymaster::Keymaster() {
-    ::ndk::SpAIBinder binder(AServiceManager_getService(keystore2_service_name));
+    ::ndk::SpAIBinder binder(AServiceManager_waitForService(keystore2_service_name));
     auto keystore2Service = ks2::IKeystoreService::fromBinder(binder);
 
     if (!keystore2Service) {