Cleanup sundry clang warnings for code that is no longer upstream

[sbruno]

Summary

Minor cleanup to quiesce some rando warnings.

[sbruno]

This code no longer appears in the upstream version: https://github.com/illumos/illumos-gate/edit/master/usr/src/lib/libzfs/common/libzfs_sendrecv.c

Patch our version of it to quiesce warnings until someone decides to sync up our code:

cc -target i386-unknown-freebsd12.0 --sysroot=/var/tmp/home/sbruno/bsd/fbsd_head/i386.i386/tmp -B/var/tmp/home/sbruno/bsd/fbsd_head/i386.i386/tmp/usr/bin  -O2 -pipe -DZFS_NO_ACL -I/home/sbruno/bsd/fbsd_head/sbin/mount -I/home/sbruno/bsd/fbsd_head/sys/cddl/compat/opensolaris -I/home/sbruno/bsd/fbsd_head/cddl/compat/opensolaris/include -I/home/sbruno/bsd/fbsd_head/cddl/compat/opensolaris/lib/libumem -I/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libzpool/common -I/home/sbruno/bsd/fbsd_head/sys/cddl/contrib/opensolaris/common/zfs -I/home/sbruno/bsd/fbsd_head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs -I/home/sbruno/bsd/fbsd_head/sys/cddl/contrib/opensolaris/uts/common/sys -I/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/head -I/home/sbruno/bsd/fbsd_head/sys/cddl/contrib/opensolaris/uts/common -I/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libnvpair -I/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libuutil/common -I/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libzfs/common -I/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libzfs_core/common -I/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libcmdutils   -DNEED_SOLARIS_BOOLEAN -g -MD  -MF.depend.libzfs_sendrecv.o -MTlibzfs_sendrecv.o -std=iso9899:1999 -fstack-protector-strong -Wno-pointer-sign -Wno-unknown-pragmas -Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable -Wno-tautological-compare -Wno-unused-value -Wno-parentheses-equality -Wno-unused-function -Wno-enum-conversion -Wno-unused-local-typedef -Wno-address-of-packed-member -Wno-switch -Wno-switch-enum -Wno-knr-promoted-parameter -Wno-parentheses  -Qunused-arguments  -c /home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_sendrecv.c -o libzfs_sendrecv.o
/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_sendrecv.c:2555:30: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                                sprintf(guidname, "%lu", thisguid);
                                                   ~~~   ^~~~~~~~
                                                   %llu
/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_sendrecv.c:2612:29: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                        sprintf(guidname, "%lu", parent_fromsnap_guid);
                                           ~~~   ^~~~~~~~~~~~~~~~~~~~
                                           %llu
/home/sbruno/bsd/fbsd_head/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_sendrecv.c:2645:29: warning: format specifies type 'unsigned long' but the argument has type 'uint64_t' (aka 'unsigned long long') [-Wformat]
                        sprintf(guidname, "%lu", parent_fromsnap_guid);
                                           ~~~   ^~~~~~~~~~~~~~~~~~~~
                                           %llu