Fix circle release.

Use a custom exec id because circle ci is failing to remove containers, which
results in a container name conflcit when trying to create the container to build
the binary.

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

circle.yml

@@ -23,4 +23,4 @@ test:
 deployment:
   release:
     tag: /v[0-9]+(\.[0-9]+)*/
-    commands: ['circle/dobi release']
+    commands: ['DOBI_EXEC_ID=release circle/dobi release']