fix(dracut-functions.sh): check_kernel_module should follow dracutsys…

…rootdir

check_kernel_module calls modprobe and tries to dry-run a module load to
check if a module is available. modprobe supports `-d` to specify a
rootdir, so just pass dracutsysrootdir to it to make it work as expected
when building initramfs for another rootfs.

Signed-off-by: Kairui Song <kasong@tencent.com>

dracut-functions.sh

@@ -731,7 +731,7 @@ check_kernel_config() {
 # 0 if the kernel module is either built-in or available
 # 1 if the kernel module is not enabled
 check_kernel_module() {
-    modprobe -S "$kernel" --dry-run "$1" &> /dev/null || return 1
+    modprobe -d "$dracutsysrootdir" -S "$kernel" --dry-run "$1" &> /dev/null || return 1
 }
 
 # get_cpu_vendor