Rename settings_oslo parameter MANAGER to ENV_MANAGER

ENV_MANAGER variable will be used to activate one of
the environment managers:
ENV_MANAGER=devops - create, power on/off VM and BM nodes,
                     snapshots for libvirt VMs
ENV_MANAGER=heat   - create OpenStack heat stack
ENV_MANAGER=empty  - only for SSH to an existing environment

Change-Id: I90a59107a7fd350ecfeb821734c2dac4e351d468
diff --git a/tcp_tests/utils/gen_test_config.py b/tcp_tests/utils/gen_test_config.py
index 17360ab..6e9c85d 100755
--- a/tcp_tests/utils/gen_test_config.py
+++ b/tcp_tests/utils/gen_test_config.py
@@ -31,7 +31,7 @@
 
 CONFIG_TMPL = OrderedDict([
     ('hardware', {
-        'manager': 'heat',
+        'env_manager': 'heat',
         'current_snapshot': None
     }),
     ('underlay', {