Make auto service optional

This makes dependencies consistent and eliminates warnings of the
form:

$M2_HOME/repository/org/apache/jclouds/driver/jclouds-slf4j/2.1.0-SNAPSHOT/jclouds-slf4j-2.1.0-SNAPSHOT.jar(org/jclouds/logging/slf4j/config/SLF4JLoggingModule.class): warning: Cannot find annotation method 'value()' in type 'AutoService': class file for com.google.auto.service.AutoService not found

Reference:

https://github.com/google/auto/tree/master/service#download

openstack-glance/pom.xml

@@ -101,6 +101,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

openstack-heat/pom.xml

@@ -99,6 +99,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
     <dependency>
       <groupId>com.google.auto.value</groupId>

openstack-marconi/pom.xml

@@ -104,6 +104,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

openstack-neutron/pom.xml

@@ -110,6 +110,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
     <dependency>
       <groupId>com.google.auto.value</groupId>

openstack-poppy/pom.xml

@@ -86,6 +86,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
     <dependency>
       <groupId>com.google.auto.value</groupId>

rackspace-autoscale-uk/pom.xml

@@ -118,6 +118,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

rackspace-autoscale-us/pom.xml

@@ -117,6 +117,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

rackspace-autoscale/pom.xml

@@ -110,6 +110,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

rackspace-cloudbigdata-us/pom.xml

@@ -122,6 +122,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

rackspace-cloudbigdata/pom.xml

@@ -115,6 +115,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

rackspace-cloudnetworks-us/pom.xml

@@ -87,6 +87,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

rackspace-cloudqueues-uk/pom.xml

@@ -123,6 +123,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>
 

rackspace-cloudqueues-us/pom.xml

@@ -123,6 +123,7 @@
       <groupId>com.google.auto.service</groupId>
       <artifactId>auto-service</artifactId>
       <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
   </dependencies>