Set perf_level to kEnableTimeExceptForMutex in regression script (#8031)

Summary:
Set the perf_level in ```tools/regression_test.sh``` in order to exercise ```PerfContext``` counters in regression tests.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8031

Test Plan: Manually run the script

Reviewed By: ajkr

Differential Revision: D31508269

Pulled By: anand1976

fbshipit-source-id: 20ddfd1cbca37f1439eed2870086a86d90653b44

tools/regression_test.sh

@@ -158,7 +158,7 @@ function init_arguments {
 
   current_time=$(date +"%F-%H:%M:%S")
   RESULT_PATH=${RESULT_PATH:-"$1/results/$current_time"}
-  COMMIT_ID=`hg id -i`
+  COMMIT_ID=`git log | head -n1 | cut -c 8-`
   SUMMARY_FILE="$RESULT_PATH/SUMMARY.csv"
 
   DB_PATH=${3:-"$1/db"}
@@ -195,6 +195,7 @@ function init_arguments {
   SEED=${SEED:-$( date +%s )}
   MULTIREAD_BATCH_SIZE=${MULTIREAD_BATCH_SIZE:-128}
   MULTIREAD_STRIDE=${MULTIREAD_STRIDE:-12}
+  PERF_LEVEL=${PERF_LEVEL:-1}
 }
 
 # $1 --- benchmark name
@@ -222,6 +223,7 @@ function run_db_bench {
   db_bench_cmd="("'\$(which time)'" -p $DB_BENCH_DIR/db_bench \
       --benchmarks=$1 --db=$DB_PATH --wal_dir=$WAL_PATH \
       --use_existing_db=$USE_EXISTING_DB \
+      --perf_level=$PERF_LEVEL \
       --disable_auto_compactions \
       --threads=$threads \
       --num=$NUM_KEYS \