PREVIEW_LMS_BASE must now be set (default value does not work for both edge and…

PREVIEW_LMS_BASE must now be set (default value does not work for both edge and edx). Make this work locally as well.
https://edx.lighthouseapp.com/projects/102637/tickets/331

cms/envs/aws.py

@@ -81,6 +81,7 @@ with open(ENV_ROOT / CONFIG_PREFIX + "env.json") as env_file:
     ENV_TOKENS = json.load(env_file)
 
 LMS_BASE = ENV_TOKENS.get('LMS_BASE')
+MITX_FEATURES['PREVIEW_LMS_BASE'] = ENV_TOKENS.get('PREVIEW_LMS_BASE')
 
 SITE_NAME = ENV_TOKENS['SITE_NAME']
 

cms/envs/common.py

@@ -41,6 +41,7 @@ MITX_FEATURES = {
 
     # Enable URL that shows information about the status of variuous services
     'ENABLE_SERVICE_STATUS': False,
+    'PREVIEW_LMS_BASE' : None
 }
 ENABLE_JASMINE = False
 

cms/envs/dev.py

@@ -55,6 +55,7 @@ DATABASES = {
 }
 
 LMS_BASE = "localhost:8000"
+MITX_FEATURES['PREVIEW_LMS_BASE'] = "localhost:8000"
 
 REPOS = {
     'edx4edx': {

cms/envs/test.py

@@ -82,6 +82,7 @@ DATABASES = {
 }
 
 LMS_BASE = "localhost:8000"
+MITX_FEATURES['PREVIEW_LMS_BASE'] = "localhost:8000"
 
 CACHES = {
     # This is the cache used for most things. Askbot will not work without a