CFile::TryExLock(): Use O_RDWR by default

Getting an exclusive lock on a file with TryExLock() requires write access,
therefor O_RDONLY is wrong here.

This worked back when we were using flock() for file locking, because flock()
doesn't need write access for an exclusive locks.

This fixes a bug where "--makeconf" claims that there is already a znc instance
running on the config file. This happened because it mis-interpreted the -EBADF
error from fcntl() as "something else already has a lock".

Signed-off-by: Uli Schlachter <psychon@znc.in>

FileUtils.h

@@ -110,7 +110,7 @@ public:
 	void Close();
 	void ClearBuffer();
 
-	bool TryExLock(const CString& sLockFile, int iFlags = O_RDONLY | O_CREAT);
+	bool TryExLock(const CString& sLockFile, int iFlags = O_RDWR | O_CREAT);
 	bool TryExLock();
 	bool ExLock();
 	bool UnLock();