Update Dockerfile

.azure-pipelines/docker-sonic-vs/Dockerfile

@@ -11,7 +11,7 @@ COPY ["debs", "/debs"]
 # Docker's diff detection mechanism, where only the file size and the modification timestamp (which will remain the
 # same, even though contents have changed) are checked between the previous and current layer.
 RUN dpkg --purge libswsscommon python3-swsscommon sonic-db-cli libsaimetadata libsairedis libsaivs syncd-vs swss sonic-eventd libdashapi
-
+RUN apt-get update
 RUN apt install /debs/libdashapi_1.0.0_amd64.deb \
                 /debs/libswsscommon_1.0.0_amd64.deb \
                 /debs/python3-swsscommon_1.0.0_amd64.deb \
@@ -24,8 +24,6 @@ RUN apt install /debs/libdashapi_1.0.0_amd64.deb \
 
 RUN if [ "$need_dbg" = "y" ] ; then dpkg -i /debs/swss-dbg_1.0.0_amd64.deb ; fi
 
-RUN apt-get update
-
 RUN apt-get -y install software-properties-common libdatetime-perl libcapture-tiny-perl build-essential libcpanel-json-xs-perl git
 
 RUN git clone -b v2.0 --single-branch --depth 1 https://github.com/linux-test-project/lcov && cd lcov && make install