Change the current directory to the DROONGA_BASE_DIR before running.
Change the current directory to the DROONGA_BASE_DIR before running.

Because some functions (ex. downloading "serf" binary) fails to write files under the current directory "/" even if we spe
cify DROONGA_BASE_DIR via the environment, we have to do "cd".

droonga/droonga-http-server,droonga/droonga-http-server,droonga/droonga-http-server