trivial: fix typo 'an host'

In English, unlike in French, the 'h' in 'host' is pronounced, meaning that
the article should be 'a' instead of 'an'.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>