Fix incorrect core file found in run_tests.sh (#2614)

test/run_tests.sh

@@ -15,11 +15,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# turn on coredumps
+ulimit -c unlimited
+rm core.*
+
 test_num=0
 failed_test=""
 rc=0
 test_bins="test_butil test_bvar bthread*unittest brpc*unittest"
-ulimit -c unlimited # turn on coredumps
 for test_bin in $test_bins; do
     test_num=$((test_num + 1))
     >&2 echo "[runtest] $test_bin"
@@ -34,6 +37,7 @@ if [ $test_num -eq 0 ]; then
     >&2 echo "[runtest] Cannot find any tests"
     exit 1
 fi
+
 print_bt () {
     # find newest core file
     COREFILE=$(find . -name "core*" -type f -printf "%T@ %p\n" | sort -k 1 -n | cut -d' ' -f 2- | tail -n 1)
@@ -42,6 +46,7 @@ print_bt () {
         gdb -c "$COREFILE" $1 -ex "thread apply all bt" -ex "set pagination 0" -batch;
     fi
 }
+
 if [ -z "$failed_test" ]; then
     >&2 echo "[runtest] $test_num succeeded"
 elif [ $test_num -gt 1 ]; then