systemd: import: expand $ZPOOL_IMPORT_OPTS correctly

Turns out $ZPOOL_IMPORT_OPTS expands in a shell-like fashion,
yielding 'import' '-aN' '-o' 'cachefile=none' for an unset variable,
and 'import' '-aN' '-o' 'cachefile=none' 'word1' 'word2' for a
white-spaced one, but ${ZPOOL_IMPORT_OPTS} expands like "${Z_I_O}"
would in a shell, yielding 'import' '-aN' '-o' 'cachefile=none' ''
(empty) and 'import' '-aN' '-o' 'cachefile=none' 'word1 word2' (spaced)

Fixes eec5ba1 "dracut: 90zfs: respect
zfs_force=1 on systemd systems"

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: John Kennedy <[email protected]>
Signed-off-by: Ahelenia Ziemiańska <[email protected]>
Closes: #12231

Author: nabijaczleweli

etc/systemd/system/zfs-import-cache.service.in

@@ -14,7 +14,7 @@ ConditionPathIsDirectory=/sys/module/zfs
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStart=@sbindir@/zpool import -c @sysconfdir@/zfs/zpool.cache -aN ${ZPOOL_IMPORT_OPTS}
+ExecStart=@sbindir@/zpool import -c @sysconfdir@/zfs/zpool.cache -aN $ZPOOL_IMPORT_OPTS
 
 [Install]
 WantedBy=zfs-import.target

etc/systemd/system/zfs-import-scan.service.in

@@ -13,7 +13,7 @@ ConditionPathIsDirectory=/sys/module/zfs
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStart=@sbindir@/zpool import -aN -o cachefile=none ${ZPOOL_IMPORT_OPTS}
+ExecStart=@sbindir@/zpool import -aN -o cachefile=none $ZPOOL_IMPORT_OPTS
 
 [Install]
 WantedBy=zfs-import.target