Fix systemd-import services

On debian, systemd complains about missing /bin/awk because it actually
is located at /usr/bin/awk. It is not a good idea to hardcode binary
paths because different linux distros use different paths. According to
systemd's man page it is absolutely safe to miss paths for binaries located
at standard locations (/bin, /sbin, /usr/bin, ...).

Further, replace this more or less complicated awk command by grep.

Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>

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

@@ -13,7 +13,7 @@ ConditionPathExists=@sysconfdir@/zfs/zpool.cache
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=@sbindir@/zpool import -c @sysconfdir@/zfs/zpool.cache -aN
-ExecStartPost=/bin/sh -c "/bin/systemctl set-environment BOOTFS=$(@sbindir@/zpool list -H -o bootfs | /bin/awk '$1 != \"-\" {print; exit}')"
+ExecStartPost=/bin/sh -c "/bin/systemctl set-environment BOOTFS=$(@sbindir@/zpool list -H -o bootfs | grep -m1 -v '^-$')"
 
 [Install]
 WantedBy=zfs-import.target

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

@@ -12,7 +12,7 @@ ConditionPathExists=!@sysconfdir@/zfs/zpool.cache
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=@sbindir@/zpool import -aN -o cachefile=none
-ExecStartPost=/bin/sh -c "/bin/systemctl set-environment BOOTFS=$(@sbindir@/zpool list -H -o bootfs | /bin/awk '$1 != \"-\" {print; exit}')"
+ExecStartPost=/bin/sh -c "/bin/systemctl set-environment BOOTFS=$(@sbindir@/zpool list -H -o bootfs | grep -m1 -v '^-$')"
 
 [Install]
 WantedBy=zfs-import.target