On client shutdown write directly into "peers.dat"...

...and not into a temporary file which gets renamed to "peers.dat" later.
This prevents softlinks from being replaced by a "real" file, see http://jira.darkcoin.qa/browse/DRK-122

Update of https://github.com/darkcoin/darkcoin/pull/63 to the new Bitcoin codebase.
Merge pull request #73 from crowning-/patch-6

On client shutdown write directly into "peers.dat"...