ci: install gcovr via apt

Change-Id: I83a16e080145e206a08cc5255a906e41605ceca8
refs: #4771

.jenkins.d/00-deps.sh

@@ -28,8 +28,7 @@ if has Ubuntu $NODE_LABELS; then
                              libsqlite3-dev libssl-dev libpcap-dev libsystemd-dev
 
     if [[ $JOB_NAME == *"code-coverage" ]]; then
-        sudo apt-get -qy install lcov libgd-perl python-setuptools
-        sudo easy_install --upgrade gcovr
+        sudo apt-get -qy install gcovr lcov libgd-perl
     fi
 fi
 

.jenkins.d/README.md

@@ -27,7 +27,7 @@ Environment Variables Used in Build Scripts
   Possible values:
 
   * empty: default build process
-  * `code-coverage` (Linux OS is assumed): debug build with tests and code coverage analysis
+  * `code-coverage` (Ubuntu Linux is assumed): debug build with tests and code coverage analysis
   * `limited-build`: only a single debug build with tests
 
 - `CACHE_DIR`: the variable defines a path to folder containing cached files from previous builds,