[explorers] Improve *BSD support.

cpu_cores and memory did lacked support for other BSDs.

cdist/conf/explorer/cpu_cores

@@ -32,6 +32,10 @@ case "$os" in
         sysctl -n hw.ncpuonline
     ;;
 
+    "freebsd"|"netbsd")
+        sysctl -n hw.ncpu
+    ;;
+
     *)
         if [ -r /proc/cpuinfo ]; then
             cores="$(grep "core id" /proc/cpuinfo | sort | uniq | wc -l)"

cdist/conf/explorer/memory

@@ -29,7 +29,7 @@ case "$os" in
         echo "$(sysctl -n hw.memsize)/1024" | bc
     ;;
 
-    "openbsd")
+    *"bsd")
         echo "$(sysctl -n hw.physmem) / 1048576" | bc
     ;;