In DoExitTasks() skip 'sleep 3' when all went well

[jsmeix]

• Type: Enhancement

• Impact: Low

• How was this pull request tested?

Before:

# time usr/sbin/rear help
...
Use 'rear -v help' for more advanced commands.
[here nothing happens for 3 seconds]

real    0m3.690s
user    0m0.629s
sys     0m0.254s

With the change of this pull request:

# time usr/sbin/rear help
...
Use 'rear -v help' for more advanced commands.

real    0m0.686s
user    0m0.644s
sys     0m0.234s

• Brief description of the changes in this pull request:

In the DoExitTasks function skip 'sleep 3'
when all went well and DoExitTasks is called at normal exit
to avoid needless 3 seconds delay of normal end of program.

[schlomo]

Big thanks @jsmeix - I was already annoyed by that delay.

[jsmeix]

@schlomo
thank you for your review!

@rear/contributors
I will merge it today afternoon unless objections appear.