package/apache: atomic creation of pid file.

package/apache: atomic creation of pid file.

The original pattern for creating the pid file was:
open_create(pid_file)
write(pid_file, pid)
close(pid_file)

But if a power outage occurs between open_create and write, the file will
be empty and httpd will refuse to start afterwards unless the corrupt pid
file is removed.

This patch uses the pattern:
open_create(temp_pid_file)
write(temp_pid_file)
close(temp_pid_file)
rename(temp_pid_file, pid_file)
which is guaranteed to be atomic, provided that temp_pid_file and pid_file
are located in the same file system, which this patch does by creating
a temporary file name with the pattern:
    pid_file_name + random_suffix

Patch is upstream as of
https://github.com/apache/httpd/commit/dd10a9352e87a868ad527022bbafdc3b82cc6d0a,
which will be in the next 2.5.x version.

Signed-off-by: Nicolas Carrier <nicolas.carrier@orolia.com>
[Thomas: update to use upstreamed patch.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>