Fix grammatical mistake, Changed character from "an" to "a"

Change-Id: I3b5fef64eb5032333060763a7438ad7a85f88d68

manila/api/views/availability_zones.py

@@ -21,7 +21,7 @@ class ViewBuilder(common.ViewBuilder):
     _collection_name = "availability_zones"
 
     def _detail(self, availability_zone):
-        """Detailed view of an single availability zone."""
+        """Detailed view of a single availability zone."""
         keys = ('id', 'name', 'created_at', 'updated_at')
         return {key: availability_zone.get(key) for key in keys}
 

manila/api/views/security_service.py

@@ -31,7 +31,7 @@ class ViewBuilder(common.ViewBuilder):
         return self._list_view(self.detail, request, security_services)
 
     def summary(self, request, security_service):
-        """Generic, non-detailed view of an security service."""
+        """Generic, non-detailed view of a security service."""
         return {
             'security_service': {
                 'id': security_service.get('id'),

manila/api/views/shares.py

@@ -36,7 +36,7 @@ class ViewBuilder(common.ViewBuilder):
         return self._list_view(self.detail, request, shares)
 
     def summary(self, request, share):
-        """Generic, non-detailed view of an share."""
+        """Generic, non-detailed view of a share."""
         return {
             'share': {
                 'id': share.get('id'),