Galera: mysql can't write into the mktemp created file

Hello all!

The galera resource agent has a problem determining the last cluster commit id because the mysql can't write to the temporary created file using mktemp.
For example:
local tmp=$(mktemp) is creating the temp file with root u+rw:
`-rw------- 1 root root 0 Feb 28 13:21 tmp.Q5LAsdR8EE`

Now the mysqld_safe process, which is usually running under other user like "mysql" can't write it's log in this file!

Not sure if thats a normal issue on all distris but its a problem on our centos 6 machine.

This is my fix for that issue using the current master:

~~~~
--- galera.orig 2017-02-28 13:18:39.274026052 +0100
+++ galera 2017-02-28 13:18:46.530401104 +0100
@@ -519,7 +519,7 @@
ocf_log info "attempting to detect last commit version by reading ${OCF_RESKEY_datadir}/grastate.dat"
last_commit="$(cat ${OCF_RESKEY_datadir}/grastate.dat | sed -n 's/^seqno.\s*\(.*\)\s*$/\1/p')"
if [ -z "$last_commit" ] || [ "$last_commit" = "-1" ]; then
- local tmp=$(mktemp)
+ local tmp=$(sudo -u $OCF_RESKEY_user mktemp)

# if we pass here because grastate.dat doesn't exist,
# try not to bootstrap from this node if possible
~~~~

Start in the Galera resource agent around the mktemp call used when grastate.dat has no usable last commit, and review how mysqld_safe runs under OCF_RESKEY_user. Reproduce the permission failure on the reported CentOS 6 setup, then verify that the temporary file can be written by the MySQL user and last-commit detection completes successfully.

Written by the indexing model from the issue text.