Add ability to change client_body_buffer_size parameter value

Related: PROD-28629

Change-Id: I1862fda645bf8a79aa7d0364d8fe659568c4bfa5
diff --git a/nginx/files/proxy.conf b/nginx/files/proxy.conf
index ca69367..12fd60c 100644
--- a/nginx/files/proxy.conf
+++ b/nginx/files/proxy.conf
@@ -42,11 +42,13 @@
 
       {%- if location.size is defined %}
       client_max_body_size {{ location.size }};
-      {%- if location.size.split("m")[0] | int > 200 %}
+        {%- if location.buffer_size is defined %}
+      client_body_buffer_size {{ location.buffer_size }};
+        {%- elif location.size.split("m")[0] | int > 200 %}
       client_body_buffer_size 200m;
-      {%- else %}
+        {%- else %}
       client_body_buffer_size 20m;
-      {%- endif %}
+        {%- endif %}
       {%- else %}
       client_max_body_size 20m;
       client_body_buffer_size 20m;
diff --git a/tests/pillar/proxy_with_ssl.sls b/tests/pillar/proxy_with_ssl.sls
index 824fa07..e1d0a8d 100644
--- a/tests/pillar/proxy_with_ssl.sls
+++ b/tests/pillar/proxy_with_ssl.sls
@@ -251,6 +251,7 @@
             port: 80
             protocol: http
             size: 10000m
+            buffer_size: 20m
             timeout: 43200
             websocket: true
             request_buffer: false