lint: silence deadcode warnings

Apprently we have had deadcode which is now being picked up by latest
MSRV lint. Created issue to evaluate it coreos#1085.

src/providers/ibmcloud_classic/mod.rs

@@ -46,6 +46,7 @@ pub struct IBMClassicProvider {
 pub struct MetaDataJSON {
     /// Fully-Qualified Domain Name (FQDN).
     #[serde(rename = "hostname")]
+    #[allow(dead_code)]
     pub fqdn: String,
     /// Local hostname.
     #[serde(rename = "name")]
@@ -54,6 +55,7 @@ pub struct MetaDataJSON {
     #[serde(rename = "uuid")]
     pub instance_id: String,
     /// SSH public keys.
+    #[allow(dead_code)]
     pub public_keys: HashMap<String, String>,
 }
 
@@ -78,9 +80,11 @@ pub struct NetLinkJSON {
 #[derive(Debug, Deserialize)]
 pub struct NetNetworkJSON {
     /// Unique network ID.
+    #[allow(dead_code)]
     pub id: String,
     /// Network type (e.g. `ipv4`)
     #[serde(rename = "type")]
+    #[allow(dead_code)]
     pub kind: String,
     /// Reference to the underlying interface (see `NetLinkJSON.id`)
     pub link: String,

src/providers/openstack/configdrive.rs

@@ -40,6 +40,7 @@ pub struct MetadataOpenstackJSON {
     /// Instance ID.
     pub uuid: Option<String>,
     /// Availability zone.
+    #[allow(dead_code)]
     pub availability_zone: Option<String>,
     /// Local hostname.
     pub hostname: Option<String>,

src/providers/powervs/mod.rs

@@ -44,6 +44,7 @@ pub struct PowerVSProvider {
 pub struct MetaDataJSON {
     /// Fully-Qualified Domain Name (FQDN).
     #[serde(rename = "hostname")]
+    #[allow(dead_code)]
     pub fqdn: String,
     /// Local hostname.
     #[serde(rename = "name")]