Add ShellCheck's --enable=all inside etc/

Strengthen static code analysis for shell scripts.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: szubersk <szuberskidamian@gmail.com>
Closes #12913

etc/init.d/Makefile.am

@@ -7,4 +7,5 @@ init_SCRIPTS = zfs-import zfs-load-key zfs-mount zfs-share zfs-zed
 
 SUBSTFILES += $(init_SCRIPTS)
 
-SHELLCHECK_SHELL = dash # local variables
+SHELLCHECK_SHELL = dash
+SHELLCHECK_OPTS = --enable=all

etc/init.d/zfs-import.in

@@ -1,4 +1,5 @@
 #!@DEFAULT_INIT_SHELL@
+# shellcheck disable=SC2154
 #
 # zfs-import    This script will import ZFS pools
 #

etc/init.d/zfs-load-key.in

@@ -1,4 +1,5 @@
 #!@DEFAULT_INIT_SHELL@
+# shellcheck disable=SC2154
 #
 # zfs-load-key  This script will load/unload the zfs filesystems keys.
 #

etc/init.d/zfs-mount.in

@@ -1,4 +1,5 @@
 #!@DEFAULT_INIT_SHELL@
+# shellcheck disable=SC2154
 #
 # zfs-mount     This script will mount/umount the zfs filesystems.
 #
@@ -68,7 +69,7 @@ do_mount()
 	check_boolean "$DO_OVERLAY_MOUNTS" && overlay=O
 
 	zfs_action "Mounting ZFS filesystem(s)" \
-	    "$ZFS" mount -a$verbose$overlay "$MOUNT_EXTRA_OPTIONS"
+	    "$ZFS" mount "-a$verbose$overlay" "$MOUNT_EXTRA_OPTIONS"
 
 	# Require each volume/filesystem to have 'noauto' and no fsck
 	# option. This shouldn't really be necessary, as long as one

etc/init.d/zfs-share.in

@@ -1,4 +1,5 @@
 #!@DEFAULT_INIT_SHELL@
+# shellcheck disable=SC2154
 #
 # zfs-share     This script will network share zfs filesystems and volumes.
 #

etc/init.d/zfs-zed.in

@@ -1,4 +1,5 @@
 #!@DEFAULT_INIT_SHELL@
+# shellcheck disable=SC2154
 #
 # zfs-zed
 #