init: Fixing dmidecode weirdness

On some old version of dmidecode, we do have some comments inside the
output like :

[root@system]: dmidecode -s system-serial-number
 #SMBIOS implementations newer than version 2.7 are not
 # fully supported
 CZJ402072W

This is pretty weird as we use this value to name some file.
Let's filter out this weird output