Update Azure Auth plugin (#8814)

Adds support for user-assigned identities

go.mod

@@ -71,7 +71,7 @@ require (
 	github.com/hashicorp/raft v1.1.2-0.20191002163536-9c6bd3e3eb17
 	github.com/hashicorp/raft-snapshot v1.0.2-0.20190827162939-8117efcc5aab
 	github.com/hashicorp/vault-plugin-auth-alicloud v0.5.5
-	github.com/hashicorp/vault-plugin-auth-azure v0.5.5
+	github.com/hashicorp/vault-plugin-auth-azure v0.5.6-0.20200422235613-1b5c70f9ef68
 	github.com/hashicorp/vault-plugin-auth-centrify v0.5.5
 	github.com/hashicorp/vault-plugin-auth-cf v0.5.4
 	github.com/hashicorp/vault-plugin-auth-gcp v0.6.1

go.sum

@@ -394,8 +394,8 @@ github.com/hashicorp/serf v0.8.3 h1:MWYcmct5EtKz0efYooPcL0yNkem+7kWxqXDi/UIh+8k=
 github.com/hashicorp/serf v0.8.3/go.mod h1:UpNcs7fFbpKIyZaUuSW6EPiH+eZC7OuyFD+wc1oal+k=
 github.com/hashicorp/vault-plugin-auth-alicloud v0.5.5 h1:JYf3VYpKs7mOdtcwZWi73S82oXrC/JR7uoPVUd8c4Hk=
 github.com/hashicorp/vault-plugin-auth-alicloud v0.5.5/go.mod h1:sQ+VNwPQlemgXHXikYH6onfH9gPwDZ1GUVRLz0ZvHx8=
-github.com/hashicorp/vault-plugin-auth-azure v0.5.5 h1:kN79ai+aMVU9hUmwscHjmweW2fGa8V/t+ScIchPZGrk=
-github.com/hashicorp/vault-plugin-auth-azure v0.5.5/go.mod h1:RCVBsf8AJndh4c6iGZtvVZFui9SG0Bj9fnF0SodNIkw=
+github.com/hashicorp/vault-plugin-auth-azure v0.5.6-0.20200422235613-1b5c70f9ef68 h1:o4ekpvOmfRxCYE7+g4dV6FQc9H+Sl1jv4JoGDrLDKt0=
+github.com/hashicorp/vault-plugin-auth-azure v0.5.6-0.20200422235613-1b5c70f9ef68/go.mod h1:RCVBsf8AJndh4c6iGZtvVZFui9SG0Bj9fnF0SodNIkw=
 github.com/hashicorp/vault-plugin-auth-centrify v0.5.5 h1:YXxXt6o6I1rOkYW+hADK0vd+uVMj4C6Qs3jBrQlKQcY=
 github.com/hashicorp/vault-plugin-auth-centrify v0.5.5/go.mod h1:GfRoy7NHsuR/ogmZtbExdJXUwbfwcxPrS9xzkyy2J/c=
 github.com/hashicorp/vault-plugin-auth-cf v0.5.4 h1:2wl+qK7cLpr4u/lkv5DgvkNoKKhHC69H1QmoXOnArLw=