Multiple $mogilefs_path variables

Greetings!

This patch for nginx mogilefs module implements multiple $mogilefs_path
variables.

They names are $mogilefs_path, $mogilefs_path1 … $mogilefs_path9

This allows to implement failover in nginx when a storage node fails.

Example:

location /download/ {
[…]

mogilefs_noverify on;
mogilefs_pass {
    proxy_pass $mogilefs_path;
    proxy_buffering off;
    error_page 502 503 504 = @failover1;
}

}

location @failover1 {
if($mogilefs_path1 = “”) {
return 503;
}

proxy_pass $mogilefs_path1;
proxy_buffering off;
error_page 502 503 504 = @failover2;

}

location @failover2 {
if($mogilefs_path2 = “”) {
return 503;
}

proxy_pass $mogilefs_path2;
proxy_buffering off;

[ ... and so on ... ]

}

When mogilefs_noverify on directive is accompanied with such
configuration, MogileFS tracker will be able to return paths to file
without verifying storage node’s live status, which theoretically makes
it reply faster.

It will be nice if someone can test it.