crash after interrupted SST
if PXC Pod was restarted during SST the /var/lib/mysql/sst-xb-tmpdir
directory become preserved. Every new SST failed if directory exists.
```
2020-06-23T20:05:34.526984Z 0 [ERROR] [WSREP-SST] FATAL: Found existing /var/lib/mysql//sst-xb-tmpdir
2020-06-23T20:05:34.527007Z 0 [ERROR] [WSREP-SST] Please remove it or specify alternative temporary directory location by setting [sst]/tmpdir
```
@@ -318,8 +318,11 @@ if [ -z "$CLUSTER_JOIN" ] && [ "$1" = 'mysqld' -a -z "$wantHelp" ]; then
fi
if [ "$1" = 'mysqld' -a -z "$wantHelp" ]; then
+ DATADIR=$(_get_config 'datadir' "$@")
+ SST_DIR=$(_get_cnf_config sst tmpdir "${DATADIR}/sst-xb-tmpdir")
+ rm -rvf "${SST_DIR}"
+
"$@" --version | tee /tmp/version_info
- DATADIR="$(_get_config 'datadir' "$@")"
if [ -f "$DATADIR/version_info" ] && ! diff /tmp/version_info "$DATADIR/version_info"; then
SOCKET="$(_get_config 'socket' "$@")"
"$@" --skip-networking --socket="${SOCKET}" --wsrep-provider='none' &
