[packages] transmission: set ulimit for open files

[packages] transmission: set ulimit for open files

Currently, transmission daemon allows you to set the max number of open
files, but it can be more than allowed by the system, thus resulting in
errors if transmission uses more than set in ulimit. The following is
a patch to compare ulimit vs open_file_limit from /etc/config/transmission.
If the open_file_limit is greater than `ulimit -n`, then invoke
ulimit -n open_file_limit + 8 (since transmission's open file limit any
seems to pertain only to open torrent files)

Signed-off-by: Joe Roback <joe at roback.cc>
git-svn-id: svn://svn.openwrt.org/openwrt/packages@25991 3c298f89-4303-0410-b956-a3cf2f4a3e73