kernel-install: skip to read /etc/machine-info in test

We do not provide any way to override /etc/machine-info.
As the file is deprecated in kernel-install, let's skip to read it when
we test kernel-install.

Fixes #28011.

src/kernel-install/test-kernel-install.sh

@@ -47,6 +47,7 @@ export BOOT_MNT="$D/boot"
 export MACHINE_ID='3e0484f3634a418b8e6a39e8828b03e3'
 export KERNEL_INSTALL_UKIFY="$ukify"
 export KERNEL_INSTALL_BOOT_STUB="$boot_stub"
+export KERNEL_INSTALL_READ_MACHINE_INFO="no"
 
 # Test type#1 installation
 "$kernel_install" -v add 1.1.1 "$D/sources/linux" "$D/sources/initrd"