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-jail.8

@@ -41,7 +41,7 @@
 .Dt ZFS-JAIL 8
 .Os FreeBSD
 .Sh NAME
-.Nm zfs Ns Pf - Cm jail
+.Nm zfs-jail
 .Nd Attaches and detaches ZFS filesystems from FreeBSD jails.
 .No A Tn ZFS
 dataset can be attached to a jail by using the
@@ -72,16 +72,16 @@ After a dataset is attached to a jail and the jailed property is set, a jailed
 file system cannot be mounted outside the jail, since the jail administrator
 might have set the mount point to an unacceptable value.
 .Sh SYNOPSIS
-.Nm
+.Nm zfs
 .Cm jail
 .Ar jailid Ns | Ns Ar jailname filesystem
-.Nm
+.Nm zfs
 .Cm unjail
 .Ar jailid Ns | Ns Ar jailname filesystem
 .Sh DESCRIPTION
 .Bl -tag -width ""
 .It Xo
-.Nm
+.Nm zfs
 .Cm jail
 .Ar jailid filesystem
 .Xc
@@ -104,7 +104,7 @@ See
 .Xr jail 8
 for more information on managing jails and configuring the parameters above.
 .It Xo
-.Nm
+.Nm zfs
 .Cm unjail
 .Ar jailid filesystem
 .Xc