[sonic-slave]: Install pympler to find the memory leaks in python (#4652)

Author: pavel-shirshov

sonic-slave/Dockerfile

@@ -280,6 +280,14 @@ RUN pip install meld3 mock
 # For vs image build
 RUN pip install pexpect==4.6.0
 
+# For sonic-utilities build
+RUN pip install mockredispy==2.9.3
+RUN pip install pytest-runner==4.4
+RUN pip install setuptools==40.8.0
+
+# For sonic-swss-common testing
+RUN pip install Pympler==0.8
+
 # Install dependencies for isc-dhcp-relay build
 RUN apt-get -y build-dep isc-dhcp