mxgrub: Remove redundant exit status checks

Callers of the function sys() don't need to check the return value,
because sys() doesn't return at all if the external command fails.

Remove `and exit 1` after sys().

Closes #52

mxgrub/mxgrub

@@ -322,18 +322,18 @@ sub cmd_install {
 	update_grub_cfg();
 
 	if (has_esp) {
-		sys 'mount','-L','ESP','/boot/efi' and exit 1;
+		sys 'mount','-L','ESP','/boot/efi';
 		if (-d '/boot/efi/EFI/grub/grubx64.efi') {
 			print "GRUB for UEFI is already installed.\n";
 		}
 		else {
-			sys 'grub-install','--target=x86_64-efi','--no-nvram',$root_disk and exit 1;
+			sys 'grub-install','--target=x86_64-efi','--no-nvram',$root_disk;
 		}
-		sys 'umount','/boot/efi' and exit 1;
+		sys 'umount','/boot/efi';
 	}
 
 	if ($mbr_type ne 'GRUB') {
-		sys 'grub-install','--target=i386-pc',$root_disk and exit 1;
+		sys 'grub-install','--target=i386-pc',$root_disk;
 	} else {
 		print "GRUB is already installed in MBR.\n";
 	}