logsys: fix TOTEM logging when corosync built out of tree

If corosync is built out-of-tree (passing --srcdir to configure) then
TOTEM logging doesn't print anything.

This is caused by the source filenames (from FILE at compilation
time) having the configured path in them - in this example
../corosync/exec/totemudp.c etc. The list of totem source filenames
passed to libqb logging facility only has the basenames so the filenames
never match up as libqb does an exact string match.

I looked into fixing this in libqb but it causes a regression. We can't
simply basename() FILE at the point of calling log_printf as it's i
common also to use FILE to generate the logging source, and
using basename() on both removes the distinction between similarly named
files from different directories which could be a requirement.

Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>