Update etcd version to 3.3.12

The default version is 3.2.17 which seems to be too old.
Some external tools are not compatible with this old version.
For example, kubeadm cannot support external etcd version that is
older than 3.2.18.

This commit update the etcd version to 3.3.12 wich is the current
latest version.

Change-Id: Icfabbe580bb83a3babb98cc9fdbfb8eb388dc108
diff --git a/stackrc b/stackrc
index 53868f3..d104bea 100644
--- a/stackrc
+++ b/stackrc
@@ -737,10 +737,10 @@
 EXTRA_CACHE_URLS=""
 
 # etcd3 defaults
-ETCD_VERSION=${ETCD_VERSION:-v3.2.17}
-ETCD_SHA256_AMD64=${ETCD_SHA256_AMD64:-"0a75e794502e2e76417b19da2807a9915fa58dcbf0985e397741d570f4f305cd"}
-ETCD_SHA256_ARM64=${ETCD_SHA256_ARM64:-"0ab4621c44c79d17d94e43bd184d0f23b763a3669056ce4ae2d0b2942410a98f"}
-ETCD_SHA256_PPC64=${ETCD_SHA256_PPC64:-"69e1279c4a2a52256b78d2a8dd23346ac46b836e678b971a459f2afaef3c275e"}
+ETCD_VERSION=${ETCD_VERSION:-v3.3.12}
+ETCD_SHA256_AMD64=${ETCD_SHA256_AMD64:-"dc5d82df095dae0a2970e4d870b6929590689dd707ae3d33e7b86da0f7f211b6"}
+ETCD_SHA256_ARM64=${ETCD_SHA256_ARM64:-"170b848ac1a071fe7d495d404a868a2c0090750b2944f8a260ef1c6125b2b4f4"}
+ETCD_SHA256_PPC64=${ETCD_SHA256_PPC64:-"77f807b1b51abbf51e020bb05bdb8ce088cb58260fcd22749ea32eee710463d3"}
 # etcd v3.2.x doesn't have anything for s390x
 ETCD_SHA256_S390X=${ETCD_SHA256_S390X:-""}
 # Make sure etcd3 downloads the correct architecture