update dump/restore to use rcmdsh() instead of rcmd()

[Jim Lawson]

>Synopsis:      dump/restore still uses the deprecated rcmd() to communicate 
>with remote tape/files
>Category:      user
>Environment:
        System      : OpenBSD 7.0
        Details     : OpenBSD 7.0 (GENERIC) #6: Mon Apr  4 00:45:25 MDT 2022
                         
r...@syspatch-70-i386.openbsd.org:/usr/src/sys/arch/i386/compile/GENERIC

        Architecture: OpenBSD.i386
        Machine     : i386
>Description:
        dumprmt.c uses the deprecated rcmd() (based on the deprecated remote 
shell protocol) to communicate with remote tape drives/files.
>How-To-Repeat:
        This is a simple architecture independent source code update: replace 
rcmd() with rcmdsh(). It doesn't look like any documentation change is 
required. Diff based on -current as of 4/25/22.

$ cvs diff
cvs diff: Diffing .
Index: dumprmt.c
===================================================================
RCS file: /vcs/cvs/src/sbin/dump/dumprmt.c,v
retrieving revision 1.31
diff -u -p -r1.31 dumprmt.c
--- dumprmt.c   21 Jan 2021 00:16:36 -0000      1.31
+++ dumprmt.c   26 Apr 2022 20:58:11 -0000
@@ -136,7 +136,7 @@ rmtgetconn(void)
        } else
                tuser = name;
 
-       rmtape = rcmd(&rmtpeer, sp->s_port, name, tuser, _PATH_RMT, NULL);
+       rmtape = rcmdsh(&rmtpeer, sp->s_port, name, tuser, _PATH_RMT, NULL);
        (void)free(name);
        if (rmtape < 0)
                return;