Fix memory leak when checking player list setting

[connorhsm]

While investigating for #258, I've used Valgrind to find a memory leak relating to the PLAYER_LIST message.

Valgrind output after server setup completed and then running for ~30 seconds:

==2966== 480 bytes in 80 blocks are definitely lost in loss record 266 of 542
==2966==    at 0x48485C3: operator new[](unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==2966==    by 0x151858: stringDuplicate(char const*) (stringUtils.h:100)
==2966==    by 0x1D6BC0: trimWhitespace(char*) (stringUtils.cpp:493)
==2966==    by 0x134579: main (server.cpp:13242)

More specifically, when we periodically reload the playerListSecret setting, playerListSecret would be overwritten before being deleted:

OneLife/server/server.cpp

Line 13245 in 330d897

playerListSecret = trimmed;

While the main functionality was introduced in #207, this memory leak was introduced shortly after by #212.

To fix this, I have refactored to only read the setting when we receive a PLAYER_LIST message and free it soon after. I also removed a reference to the secret which was used to decide how long to wait until killing the socket, which I deemed unnecessary. This implementation is similar to how other secret settings are already fetched (close to when they are used).

OneLife/server/server.cpp

Lines 10812 to 10814 in 330d897

	char *reflectorSharedSecret =
	SettingsManager::
	getStringSetting( "reflectorSharedSecret" );

I have compiled the server before and after my fix, and observed Valgrind output in both cases. With the refactor applied, no memory leaks are detected. I have also tested the continued functionality of the PLAYER_LIST message with the refactor applied, Dictator was able to continue communicating without any changes or issues.

Note the current production server is using ~4GB swap (detailed in #258), which I suspect is due to this issue. It's possible this is the sole cause of #258, but further monitoring will be required.

[connorhsm]

@Eboubaker May be of interest, your input is appreciated 😄

[Eboubaker]

a classic memory leak, sorry for my oversight on this. You changed the code to always read the setting file playerListSecret when a request for playerList is made, this will make the password change effect immediately I think it is better that way.

[risvh]

Great find, thanks both.