find_localhost: Try both hostname and hostname -f before raising (#…

…242)

Do not explicitly use `hostname -s` (the opposite of `hostname -f`)
since it fails on Windows.

lib/dogapi/common.rb

@@ -210,14 +210,17 @@ def Dogapi.find_datadog_host
   @@hostname = nil
 
   def Dogapi.find_localhost
-    unless @@hostname
-      out, status = Open3.capture2('hostname', '-f', err: File::NULL)
-      # Get status to check if the call was successful
-      raise SystemCallError, 'Could not get hostname with `hostname -f`' unless status.exitstatus.zero?
-      @@hostname = out.strip
-    end
-  rescue SystemCallError
-    @@hostname = Addrinfo.getaddrinfo(Socket.gethostname, nil, nil, nil, nil, Socket::AI_CANONNAME).first.canonname
+    return @@hostname if @@hostname
+    out, status = Open3.capture2('hostname', '-f', err: File::NULL)
+    unless status.exitstatus.zero?
+      begin
+        out = Addrinfo.getaddrinfo(Socket.gethostname, nil, nil, nil, nil, Socket::AI_CANONNAME).first.canonname
+      rescue SocketError
+        out, status = Open3.capture2('hostname', err: File::NULL)
+        raise SystemCallError, 'Both `hostname` and `hostname -f` failed.' unless status.exitstatus.zero?
+      end
+    end
+    @@hostname = out.strip
   end
 
   def Dogapi.find_proxy