rsyslogd: Backport upstream commits to fix rsyslog segmentation fault when heavy load

Backport <commit 9a775051f7373176c6e54bee1110965342dd41ad> and
<commit 17e1ee2539cea6bac16832b488afd52b20a348ac> from rsyslog
upstream <https://github.com/rsyslog/rsyslog

> to solve issue:
rsyslog segmentation fault when heavy load.
Solve the race condition in GenerateLocalHostNameProperty between the
prop.Destruct(&propLocalHostName) and prop.Construct(&propLocalHostName).

Signed-off-by: Li Zhou <li.zhou@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>