Don't ignore return value from gethostname(3)

[trasz]

Summary

Don't ignore return value from gethostname(3). It probably
cannot happen, but it silences down Coverity.

[mav]

I have feeling it is too aggressive to exit with error here, but since it should not really happen -- OK, will count it as an assertion. May be just assert then?

[trasz]

(Tinderboxed.)

[trasz]

In D26606#592597, @mav wrote:

I have feeling it is too aggressive to exit with error here, but since it should not really happen -- OK, will count it as an assertion. May be just assert then?

Not sure how Coverity deals with asserts. Besides, I kind of like the current version.