Add missing newlines before printing the Dockerfile content (#700)

Before:
```
Dockerfile created successfully in /tmp/tmp.qyMdb0vI8X/DockerfileFROM python:3.10-slim
WORKDIR /app

RUN apt-get update && apt-get install -y        iputils-ping net-tools iproute2 dnsutils telnet        curl wget telnet        procps psmisc lsof        traceroute        bubblewrap        && rm -rf /var/lib/apt/lists/*
```

After:
```
Dockerfile created successfully in /tmp/tmp.qyMdb0vI8X/Dockerfile

FROM python:3.10-slim
WORKDIR /app

RUN apt-get update && apt-get install -y        iputils-ping net-tools iproute2 dnsutils telnet        curl wget telnet        procps psmisc lsof        traceroute        bubblewrap        && rm -rf /var/lib/apt/lists/*

```

Signed-off-by: Yuan Tang <terrytangyuan@gmail.com>

llama_stack/distribution/build_container.sh

@@ -126,7 +126,7 @@ ENTRYPOINT ["python", "-m", "llama_stack.distribution.server.server", "--templat
 
 EOF
 
-printf "Dockerfile created successfully in $TEMP_DIR/Dockerfile"
+printf "Dockerfile created successfully in $TEMP_DIR/Dockerfile\n\n"
 cat $TEMP_DIR/Dockerfile
 printf "\n"