Always use 'ps -ao' to detect commands

Previously we used 'ps -eo' for some operating systems. It turns out
flags '-ao' work fine for all, and it should also be fine per posix spec

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/ps.html#tag_20_96

save_command_strategies/ps.sh

@@ -10,16 +10,8 @@ exit_safely_if_empty_ppid() {
 	fi
 }
 
-ps_command_flags() {
-	case $(uname -s) in
-		FreeBSD) echo "-ao" ;;
-		OpenBSD) echo "-ao" ;;
-		*) echo "-eo" ;;
-	esac
-}
-
 full_command() {
-	ps "$(ps_command_flags)" "ppid command" |
+	ps -ao "ppid command" |
 		sed "s/^ *//" |
 		grep "^${PANE_PID}" |
 		cut -d' ' -f2-