Mark broken DigitalOcean tests as pending

See https://github.com/fog/fog/pull/3304

tests/digitalocean/models/compute/server_tests.rb

@@ -1,5 +1,7 @@
 Shindo.tests("Fog::Compute[:digitalocean] | server model", ['digitalocean', 'compute']) do
 
+  pending # See https://github.com/fog/fog/pull/3304
+
   server  = fog_test_server
 
   tests('The server model should') do

tests/digitalocean/requests/compute/get_server_details_tests.rb

@@ -1,5 +1,7 @@
 Shindo.tests('Fog::Compute[:digitalocean] | get_server_details request', ['digitalocean', 'compute']) do
 
+  pending # See https://github.com/fog/fog/pull/3304
+
   tests('success') do
 
     test('#get_server_details') do

tests/digitalocean/requests/compute/power_cycle_server_tests.rb

@@ -1,5 +1,7 @@
 Shindo.tests('Fog::Compute[:digitalocean] | power_cycle_server request', ['digitalocean', 'compute']) do
 
+  pending # See https://github.com/fog/fog/pull/3304
+
   server = fog_test_server
 
   tests('success') do

tests/digitalocean/requests/compute/power_state_tests.rb

@@ -1,6 +1,8 @@
 Shindo.tests('Fog::Compute[:digitalocean] | power on/off/shutdown requests',
              ['digitalocean', 'compute']) do
 
+  pending # See https://github.com/fog/fog/pull/3304
+
   service = Fog::Compute[:digitalocean]
   server = fog_test_server