Some relative paths in redis.conf for vm-swap-file not working

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Using some relative paths will work in redis.conf; others will not, though 
their paths are as valid as the other specified paths (relative to cwd).

What steps will reproduce the problem?
1. Make directories ../tmp, ./config and ./tmp
2. Configure redis in ./config/redis.conf
3. Try using ./tmp/redis.swap and ../tmp/redis.swap

What is the expected output? What do you see instead?
With ./tmp/redis.swap:
[4444] 28 Dec 22:34:34 * Using 'tmp/redis.swap' as swap file
[4444] 28 Dec 22:34:34 # Can't open the swap file: No such file or directory. 
Exiting.

With ../tmp/redis.swap:
[4445] 28 Dec 22:34:43 * Using '/tmp/redis.swap' as swap file
[4445] 28 Dec 22:34:43 * Allocating 4294967296 bytes of swap file
[4445] 28 Dec 22:34:43 * Swap file allocated with success
[4445] 28 Dec 22:34:43 - Allocated 16777216 bytes page table for 134217728 pages

What version of the product are you using? On what operating system?
2.0.4 stable

Please provide any additional information below.
Ubuntu 9.04, 2.6.28-19-server, gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4)

Original issue reported on code.google.com by james.wintermute@gmail.com on 28 Dec 2010 at 10:40