fix(perl-xCAT): map the 32-bit x86 architecture to i386

genimage converts osimage.osarch with debian_arch and uses the result twice: it
picks the apt mirror and it becomes debootstrap --arch. The map knew x86_64 but
not x86, so an image with osarch=x86 selected the ports archive, which carries
no i386, and then asked debootstrap for an architecture it does not know.

Signed-off-by: Vinícius Ferrão <2031761+viniciusferrao@users.noreply.github.com>

perl-xCAT/xCAT/Utils.pm

@@ -4876,6 +4876,7 @@ sub splitkcmdline {
 # without network drivers instead of stopping at debootstrap.
 my %DEBIAN_ARCH = (
     'x86_64' => 'amd64',
+    'x86'    => 'i386',
 );
 
 sub debian_arch {