[sonic-mgmt] Call docker cmd on appropriate container in generate_tel…

…emetry_config() funct (sonic-net#11552)

Description of PR
generate_telemetry_config() function already establishes that the GNMI container is 'telemetry' so call docker supervisorctl status using this container name.

Summary:
Fixes #
aristanetworks/sonic-qual.msft#61

tests/common/helpers/gnmi_utils.py

@@ -52,7 +52,8 @@ def generate_telemetry_config(self, duthost):
                 self.gnmi_config_table = "TELEMETRY"
                 self.gnmi_container = "telemetry"
                 # GNMI program is telemetry or gnmi-native
-                res = duthost.shell("docker exec telemetry supervisorctl status", module_ignore_errors=True)
+                res = duthost.shell("docker exec %s supervisorctl status" % self.gnmi_container,
+                                    module_ignore_errors=True)
                 if 'telemetry' in res['stdout']:
                     self.gnmi_program = "telemetry"
                 else: