Properly format NAME subsection of zfs/zpool subcommands

Use proper names (i.e. zfs-allow and zpool-add) in NAME subsections
of zfs/zpool subcommands instead of current "pretty-printed" ones as
makewhatis utilities (or some implementations of it, namely the one
from mandoc suite used in FreeBSD) look not only at the document title
but also in NAME subsection, adding zfs(8)/zpool(8) to search results
which is not correct. (Common sense and other utilities splitting
subcommands in multiple man pages, e.g. git, do the same.)

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: xtouqh <xtouqh@hotmail.com>
Closes #11086

man/man8/zfs-destroy.8

@@ -34,25 +34,25 @@
 .Dt ZFS-DESTROY 8
 .Os
 .Sh NAME
-.Nm zfs Ns Pf - Cm destroy
+.Nm zfs-destroy
 .Nd Destroys the given dataset(s), snapshot(s), or bookmark.
 .Sh SYNOPSIS
-.Nm
+.Nm zfs
 .Cm destroy
 .Op Fl Rfnprv
 .Ar filesystem Ns | Ns Ar volume
-.Nm
+.Nm zfs
 .Cm destroy
 .Op Fl Rdnprv
 .Ar filesystem Ns | Ns Ar volume Ns @ Ns Ar snap Ns
 .Oo % Ns Ar snap Ns Oo , Ns Ar snap Ns Oo % Ns Ar snap Oc Oc Oc Ns ...
-.Nm
+.Nm zfs
 .Cm destroy
 .Ar filesystem Ns | Ns Ar volume Ns # Ns Ar bookmark
 .Sh DESCRIPTION
 .Bl -tag -width ""
 .It Xo
-.Nm
+.Nm zfs
 .Cm destroy
 .Op Fl Rfnprv
 .Ar filesystem Ns | Ns Ar volume
@@ -96,7 +96,7 @@ or the
 options, as they can destroy large portions of a pool and cause unexpected
 behavior for mounted file systems in use.
 .It Xo
-.Nm
+.Nm zfs
 .Cm destroy
 .Op Fl Rdnprv
 .Ar filesystem Ns | Ns Ar volume Ns @ Ns Ar snap Ns
@@ -167,7 +167,7 @@ options, as they can destroy large portions of a pool and cause unexpected
 behavior for mounted file systems in use.
 .El
 .It Xo
-.Nm
+.Nm zfs
 .Cm destroy
 .Ar filesystem Ns | Ns Ar volume Ns # Ns Ar bookmark
 .Xc