Use hw.physmem64 instead of hw.physmem for NetBSD in pkg/sys/getHwPhysmem (#10907)

"hw.physmem" only reports reasonable results on 32 bit systems and is
kept to not break binary compatibility. On other systems, it reports
"-1". "hw.phymem64" reports reasonable results on all systems.

MinIO getHwPhysmem method currently uses the deprecated 
"hw.physmem" key which results in a parse error (due to the -1).

This pull request asks for changing this. The change was tested
successfully on NetBSD/amd64 9.1.

pkg/sys/stats_bsd.go

@@ -1,4 +1,4 @@
-// +build openbsd netbsd freebsd dragonfly
+// +build openbsd freebsd dragonfly
 
 /*
  * MinIO Cloud Storage, (C) 2016,2017 MinIO, Inc.

pkg/sys/stats_netbsd.go

@@ -0,0 +1,45 @@
+// +build netbsd
+
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sys
+
+import (
+	"encoding/binary"
+	"syscall"
+)
+
+func getHwPhysmem() (uint64, error) {
+	totalString, err := syscall.Sysctl("hw.physmem64")
+	if err != nil {
+		return 0, err
+	}
+
+	// syscall.sysctl() helpfully assumes the result is a null-terminated string and
+	// removes the last byte of the result if it's 0 :/
+	totalString += "\x00"
+
+	total := uint64(binary.LittleEndian.Uint64([]byte(totalString)))
+
+	return total, nil
+}
+
+// GetStats - return system statistics for bsd.
+func GetStats() (stats Stats, err error) {
+	stats.TotalRAM, err = getHwPhysmem()
+	return stats, err
+}