switch to new go-acme imports from xenolf. Fix api changes (#540)

* switch to new go-acme imports from xenolf. Fix api changes

* update many vault related dependencies

vendor/github.com/go-acme/lego/challenge/dns01/fqdn.go

@@ -0,0 +1,19 @@
+package dns01
+
+// ToFqdn converts the name into a fqdn appending a trailing dot.
+func ToFqdn(name string) string {
+	n := len(name)
+	if n == 0 || name[n-1] == '.' {
+		return name
+	}
+	return name + "."
+}
+
+// UnFqdn converts the fqdn into a name removing the trailing dot.
+func UnFqdn(name string) string {
+	n := len(name)
+	if n != 0 && name[n-1] == '.' {
+		return name[:n-1]
+	}
+	return name
+}