Make docker_run_tests.sh pass shellcheck (with suppressions)

tools/run_tests/dockerize/docker_run_tests.sh

@@ -24,11 +24,13 @@ export PATH=$PATH:/usr/bin/llvm-symbolizer
 
 # Ensure that programs depending on current-user-ownership of cache directories
 # are satisfied (it's being mounted from outside the image).
-chown $(whoami) $XDG_CACHE_HOME
+chown "$(whoami)" "$XDG_CACHE_HOME"
 
 mkdir -p /var/local/git
 git clone  /var/local/jenkins/grpc /var/local/git/grpc
 # clone gRPC submodules, use data from locally cloned submodules where possible
+# TODO: figure out a way to eliminate this shellcheck suppression:
+# shellcheck disable=SC2016,SC1004
 (cd /var/local/jenkins/grpc/ && git submodule foreach 'cd /var/local/git/grpc \
 && git submodule update --init --reference /var/local/jenkins/grpc/${name} \
 ${name}')
@@ -52,8 +54,8 @@ echo '</body></html>' >> index.html
 cd ..
 
 zip -r reports.zip reports
-find . -name report.xml | xargs -r zip reports.zip
-find . -name sponge_log.xml | xargs -r zip reports.zip
-find . -name 'report_*.xml' | xargs -r zip reports.zip
+find . -name report.xml -print0 | xargs -0 -r zip reports.zip
+find . -name sponge_log.xml -print0 | xargs -0 -r zip reports.zip
+find . -name 'report_*.xml' -print0 | xargs -0 -r zip reports.zip
 
 exit $exit_code