Update RPC python example and tutorial to use wait_for_service_async (#733)

* Custom transport example: note about doc out of date

* Update RPC python example and tutorial to use wait_for_service_async

The new API is available since 7.5 and can be now used the latest code examples

Author: alexcamposruiz

examples/connext_dds/remote_procedure_call/py/inventory_client.py

@@ -21,21 +21,13 @@ class InventoryClient(InventoryService, rpc.ClientBase):
     ...
 
 
-async def wait_for_service(client: InventoryClient):
-    while client.matched_service_count == 0:
-        await sleep(0.1)
-
-
 async def run_client(args):
     participant = dds.DomainParticipant(args.domain)
     client = InventoryClient(
         participant, "Inventory", max_wait_per_call=dds.Duration(20)
     )
 
-    # For versions 7.4.0 and below:
-    await wait_for_service(client)
-    # For newer versions you can use the following:
-    # await client.wait_for_service_async(dds.Duration(20))
+    await client.wait_for_service_async(dds.Duration(20))
 
     print("Initial inventory: ", await client.get_inventory())
 

tutorials/rpc/py/robot_client.py

@@ -24,10 +24,7 @@ async def main():
     participant = dds.DomainParticipant(domain_id=0)
     client = RobotControlClient(participant, "MyRobotControl")
 
-    # For versions 7.4.0 and below:
-    sleep(2)
-    # For newer versions you can use the following:
-    # await client.wait_for_service_async(dds.Duration(20))
+    await client.wait_for_service_async(dds.Duration(20)) # Available in Connext 7.5.0+
 
     print("Calling walk_to...")
     result = await client.walk_to(