fix ERR unknown command 'HMSETNX'

remove race condition and improve tests.

.gitignore

@@ -13,6 +13,7 @@ plugins/c9.ide.language.javascript.tern/util/sigs_ts
 plugins/c9.account.billing/node_modules/
 plugins/c9.account/node_modules/
 plugins/c9.api.project/coverage/
+plugins/c9.db.redis/coverage/
 scripts/build
 build/output
 build/standalone/
@@ -78,4 +79,4 @@ plugins/c9.proxy/haproxy-*
 npm-debug.log
 foo.js
 hello.js
-plugins/c9.docker/containers/ci/files/github_c9_newclient
+plugins/c9.docker/containers/ci/files/github_c9_newclient