freebsd-update: for rollback, first create directories

rollback_files() tried to install files before creating the directories
for those files.  In some cases this is due to special handling to
install certain classes of files earlier than others.

Just create all directories up front when performing rollback.

PR:		273950
Reviewed by:	dim
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D42020

usr.sbin/freebsd-update/freebsd-update.sh

@@ -3191,6 +3191,11 @@ rollback_setup_rollback () {
 
 # Install old files, delete new files, and update linker.hints
 rollback_files () {
+	# Create directories first.  They may be needed by files we will
+	# install in subsequent steps (PR273950).
+	awk -F \| '{if ($2 == "d") print }' $1/INDEX-OLD > INDEX-OLD
+	install_from_index INDEX-OLD || return 1
+
 	# Install old shared library files which don't have the same path as
 	# a new shared library file.
 	grep -vE '^/boot/' $1/INDEX-NEW |