specify pip version to fix oserror 0 of proxy (#3165)

Author: glorysdj

docker/cluster-serving/Dockerfile

@@ -24,7 +24,7 @@ RUN apt-get update && \
 #python
 RUN apt-get install -y python3-minimal && \
     apt-get install -y build-essential python3 python3-setuptools python3-dev python3-pip && \
-    pip3 install --upgrade pip && \
+    pip3 install --upgrade pip==20.2.4 && \
     pip install --upgrade setuptools && \
     pip install opencv-python && \
     pip install pyyaml && \

docker/hyperzoo/Dockerfile

@@ -73,7 +73,7 @@ RUN chmod +x /sbin/tini
 #python
 RUN apt-get install -y python3-minimal && \
     apt-get install -y build-essential python3 python3-setuptools python3-dev python3-pip && \
-    pip3 install --upgrade pip && \
+    pip3 install --upgrade pip==20.2.4 && \
     pip install --upgrade setuptools && \
     pip install numpy scipy && \
     pip install --no-binary pandas==0.23.4 -I pandas && \

docker/zoo/Dockerfile

@@ -57,7 +57,7 @@ RUN wget https://enos.itcollege.ee/~jpoial/allalaadimised/jdk8/jdk-8u261-linux-x
 #python
 RUN apt-get install -y python3-minimal && \
     apt-get install -y build-essential python3 python3-setuptools python3-dev python3-pip && \
-    pip3 install --upgrade pip && \
+    pip3 install --upgrade pip==20.2.4 && \
     pip install --upgrade setuptools && \
     pip install numpy scipy && \
     pip install --no-binary pandas -I pandas && \