[AIRFLOW-6461] Remove silent flags in Dockerfile

[mik-laj]

Hello,

Sometimes I have slow internet and would like to see a progress bar. Without a progress bar, I'm afraid that Docker has hung.

Best regards

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Link to JIRA issue: https://issues.apache.org/jira/browse/AIRFLOW-6461

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[mik-laj]

For example:

+ curl -L https://archive.cloudera.com/cdh5/cdh/5/hadoop-2.6.0-cdh5.11.0.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
 15  314M   15 49.2M    0     0   801k      0  0:06:41  0:01:02  0:05:39  686k

6 minutes without any message. This is not a nice experience. I know that some people say that we have very fast internet in Warsaw, but I rent a flat, so I have internet for the price of one bottle of vodka (20 zl = 4,71 euro). We have to pay two bottles of vodka (40 zł = 9,43 zł) for very fast internet. :-D