Revert "Close urllib3 pool before swapping the server into the "inactive" list"

This reverts commit 21509d9.

Apparently, this caused some downstream havoc, specifically observable on bad
or flaky connection quality to the database.

Author: amotl

src/crate/client/http.py

@@ -584,15 +584,6 @@ def _drop_server(self, server, message):
         """
         Drop server from active list and adds it to the inactive ones.
         """
-
-        # Try to close resource first.
-        try:
-            self.server_pool[server].close()
-        except Exception as ex:
-            logger.warning("When removing server from active pool, "
-                           "resource could not be closed: %s", ex)
-
-        # Apply bookkeeping.
         try:
             self._active_servers.remove(server)
         except ValueError:
@@ -601,7 +592,7 @@ def _drop_server(self, server, message):
             heapq.heappush(self._inactive_servers, (time(), server, message))
             logger.warning("Removed server %s from active pool", server)
 
-        # If this is the last server, raise an exception.
+        # if this is the last server raise exception, otherwise try next
         if not self._active_servers:
             raise ConnectionError(
                 ("No more Servers available, "