add git branch to conda env name

Jenkinsfile

@@ -11,7 +11,7 @@ def githubUsernameToSlackName(github_author) {
 }
 
 pipeline_name="vivarium"
-conda_env_name="${pipeline_name}-${BUILD_NUMBER}"
+conda_env_name="${pipeline_name}-${GIT_BRANCH}-${BUILD_NUMBER}"
 conda_env_path="/tmp/${conda_env_name}"
 // defaults for conda and pip are a local directory /svc-simsci for improved speed.
 // In the past, we used /ihme/code/* on the NFS (which is slower)
@@ -260,4 +260,4 @@ pipeline {
       } // Python matrix bracket
     } // Python matrix stage bracket
   } // stages bracket
-} // pipeline bracket
+} // pipeline bracket