ZTS: Move dumpdev tests to sunos.run

Neither FreeBSD nor Linux support dumping to zvols.

DilOS still uses these tests, so the files are kept and the tests have
been relocated to sunos.run.

An `is_illumos` function was added to libtest.shlib to eliminate some
awkward platform checks.

A few functions that are not expected to be used outside of illumos
have been sanitized of extraneous FreeBSD adaptations.

Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes #9794

tests/zfs-tests/include/default.cfg.in

@@ -143,7 +143,7 @@ export SPA_MINDEVSIZE=$((64 * 1024 * 1024))
 # For iscsi target support
 export ISCSITGTFILE=/tmp/iscsitgt_file
 export ISCSITGT_FMRI=svc:/system/iscsitgt:default
-if ! is_linux && ! is_freebsd; then
+if is_illumos; then
 export AUTO_SNAP=$(svcs -a | grep auto-snapshot | grep online | awk \
     '{print $3}')
 fi

tests/zfs-tests/include/libtest.shlib

@@ -92,6 +92,18 @@ function is_linux
 	fi
 }
 
+# Determine if this is an illumos test system
+#
+# Return 0 if platform illumos, 1 if otherwise
+function is_illumos
+{
+	if [[ $(uname -o) == "illumos" ]]; then
+		return 0
+	else
+		return 1
+	fi
+}
+
 # Determine if this is a FreeBSD test system
 #
 # Return 0 if platform FreeBSD, 1 if otherwise