RUBY-2850 Add server selection spec test to ensure that RSGhost servers are not selectable (#2389)

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: p-mongo

spec/spec_tests/data/server_selection/Unknown/read/ghost.yml

@@ -0,0 +1,11 @@
+topology_description:
+  type: Unknown
+  servers:
+  - address: a:27017
+    avg_rtt_ms: 5
+    type: RSGhost
+operation: read
+read_preference:
+  mode: Nearest
+suitable_servers: []
+in_latency_window: []

spec/spec_tests/data/server_selection/Unknown/write/ghost.yml

@@ -0,0 +1,11 @@
+topology_description:
+  type: Unknown
+  servers:
+  - address: a:27017
+    avg_rtt_ms: 5
+    type: RSGhost
+operation: write
+read_preference:
+  mode: Nearest
+suitable_servers: []
+in_latency_window: []