sh.zio.backup: fix error not being captured

usr/local/bin/sh.zio.backup

@@ -80,6 +80,7 @@ function invoke_restic() {
         attempts_delay=600
 
         while true; do
+			set -o pipefail
         	exec 3>&1
 
             restic_out="$("$restic_path" \
@@ -102,6 +103,7 @@ function invoke_restic() {
                 fi
             fi
 
+			set +o pipefail
             exec 3>&-
         done
     fi