systemd: fix echo call with absolute path

systemd: fix echo call with absolute path

Without placing the absolute path when formatting the
nvme connect-all args we can get the following error:
--
connect-all: unrecognized option '-e'
Discover NVMeoF subsystems and connect to them  [  --transport=<LIST>, -t <LIST> ]    --- transport type
  [  --traddr=<LIST>, -a <LIST> ]       --- transport address
  [  --trsvcid=<LIST>, -s <LIST> ]      --- transport service id (e.g. IP
                                            port)
  [  --host-traddr=<LIST>, -w <LIST> ]  --- host traddr (e.g. FC WWN's)
  [  --hostnqn=<LIST>, -q <LIST> ]      --- user-defined hostnqn (if default
                                            not used)
  [  --hostid=<LIST>, -I <LIST> ]       --- user-defined hostid (if default
                                            not used)
  [  --raw=<LIST>, -r <LIST> ]          --- raw output file
  [  --device=<LIST>, -d <LIST> ]       --- use existing discovery controller
                                            device
  [  --keep-alive-tmo=<LIST>, -k <LIST> ] --- keep alive timeout period in
                                            seconds
  [  --reconnect-delay=<LIST>, -c <LIST> ] --- reconnect timeout period in
                                            seconds
  [  --ctrl-loss-tmo=<LIST>, -l <LIST> ] --- controller loss timeout period in
                                            seconds
  [  --hdr_digest, -g ]                 --- enable transport protocol header
                                            digest (TCP transport)
  [  --data_digest, -G ]                --- enable transport protocol data
                                            digest (TCP transport)
  [  --nr-io-queues=<LIST>, -i <LIST> ] --- number of io queues to use
                                            (default is core count)
  [  --nr-write-queues=<LIST>, -W <LIST> ] --- number of write queues to use
                                            (default 0)
  [  --nr-poll-queues=<LIST>, -P <LIST> ] --- number of poll queues to use
                                            (default 0)
  [  --queue-size=<LIST>, -Q <LIST> ]   --- number of io queue elements to
                                            use (default 128)
  [  --persistent, -p ]                 --- persistent discovery connection
  [  --quiet, -Q ]                      --- suppress already connected errors
Usage: nvme connect-all <device> [OPTIONS]
Options:
: nvmf-connect@--device\x3dnvme0\t--transport\x3dtcp\t--traddr\x3d192.168.123.1\t--trsvcid\x3d8009\t--host-traddr\x3dnone.service: Main process exited, code=exited, status=70/n/a
: nvmf-connect@--device\x3dnvme0\t--transport\x3dtcp\t--traddr\x3d192.168.123.1\t--trsvcid\x3d8009\t--host-traddr\x3dnone.service: Failed with result 'exit-code'.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>