Log error if it exists while serving APIs

[cesnietor]

If there's an error while serving the APIs, there's no way to know what went wrong.
This helps a bit with it.

Before:

√ console(master) % make && CONSOLE_ACCESS_KEY=minioadmin CONSOLE_SECRET_KEY=minioadmin CONSOLE_MINIO_SERVER=http://localhost:9009 CONSOLE_DEV_MODE=on ./console server
Building Console binary to './console'
?1 console(master) % 

After:

√ console(master) % make && CONSOLE_ACCESS_KEY=minioadmin CONSOLE_SECRET_KEY=minioadmin CONSOLE_MINIO_SERVER=http://localhost:9009 CONSOLE_DEV_MODE=on ./console server
Building Console binary to './console'
error serving API: listen tcp :9090: bind: address already in use
?1 console(master) %