.gitignore: allow symlinks when ignoring testlog
.gitignore: allow symlinks when ignoring testlog

The .gitignore entry for testlog/ directory is generalized
from "testlog/*" to "testlog", in order to please everyone
who potentially wants test logs to use ramfs by symlinking
testlog to /tmp. Without the change, the symlink remains
visible in `git status`.

Message-Id: <d18793d63c8b2d41e0117443dceb0d55ae582b24@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,avikivity/scylla