Enable shellcheck to run for select scripts

Enable shellcheck to run on zed scripts,
paxcheck.sh, zfs-tests.sh, zfs.sh, and zloop.sh.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes #5812

cmd/zed/zed.d/zed-functions.sh

@@ -1,3 +1,5 @@
+#!/bin/sh
+# shellcheck disable=SC2039
 # zed-functions.sh
 #
 # ZED helper functions for use in ZEDLETs
@@ -126,6 +128,7 @@ zed_lock()
     #
     eval "exec ${fd}> '${lockfile}'"
     err="$(flock --exclusive "${fd}" 2>&1)"
+    # shellcheck disable=SC2181
     if [ $? -ne 0 ]; then
         zed_log_err "failed to lock \"${lockfile}\": ${err}"
     fi
@@ -162,8 +165,8 @@ zed_unlock()
     fi
 
     # Release the lock and close the file descriptor.
-    #
     err="$(flock --unlock "${fd}" 2>&1)"
+    # shellcheck disable=SC2181
     if [ $? -ne 0 ]; then
         zed_log_err "failed to unlock \"${lockfile}\": ${err}"
     fi
@@ -424,14 +427,14 @@ zed_rate_limit()
 # Return
 #   Pool name
 #
-function zed_guid_to_pool
+zed_guid_to_pool()
 {
 	if [ -z "$1" ] ; then
 		return
 	fi
 
-	guid=$(printf "%llu" $1)
+	guid=$(printf "%llu" "$1")
 	if [ ! -z "$guid" ] ; then
-		$ZPOOL get -H -ovalue,name guid | awk '$1=='$guid' {print $2}'
+		$ZPOOL get -H -ovalue,name guid | awk '$1=='"$guid"' {print $2}'
 	fi
 }