Fix process_remote_perf_flamegraphs.sh to pass shellcheck

tools/run_tests/performance/process_remote_perf_flamegraphs.sh

@@ -13,17 +13,18 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-mkdir -p $OUTPUT_DIR
+mkdir -p "$OUTPUT_DIR"
 
-PERF_DATA_FILE=${PERF_BASE_NAME}-perf.data
-PERF_SCRIPT_OUTPUT=${PERF_BASE_NAME}-out.perf
+PERF_DATA_FILE="${PERF_BASE_NAME}-perf.data"
+PERF_SCRIPT_OUTPUT="${PERF_BASE_NAME}-out.perf"
 
 # Generate Flame graphs
 echo "running perf script on $USER_AT_HOST with perf.data"
-ssh $USER_AT_HOST "cd ~/performance_workspace/grpc && perf script -i $PERF_DATA_FILE | gzip > ${PERF_SCRIPT_OUTPUT}.gz"
+# shellcheck disable=SC2029
+ssh "$USER_AT_HOST" "cd ~/performance_workspace/grpc && perf script -i $PERF_DATA_FILE | gzip > ${PERF_SCRIPT_OUTPUT}.gz"
 
-scp $USER_AT_HOST:~/performance_workspace/grpc/$PERF_SCRIPT_OUTPUT.gz .
+scp "$USER_AT_HOST:~/performance_workspace/grpc/$PERF_SCRIPT_OUTPUT.gz" .
 
-gzip -d -f $PERF_SCRIPT_OUTPUT.gz
+gzip -d -f "$PERF_SCRIPT_OUTPUT.gz"
 
-~/FlameGraph/stackcollapse-perf.pl --kernel $PERF_SCRIPT_OUTPUT | ~/FlameGraph/flamegraph.pl --color=java --hash > ${OUTPUT_DIR}/${OUTPUT_FILENAME}.svg
+~/FlameGraph/stackcollapse-perf.pl --kernel "$PERF_SCRIPT_OUTPUT" | ~/FlameGraph/flamegraph.pl --color=java --hash > "${OUTPUT_DIR}/${OUTPUT_FILENAME}.svg"