inotify: don't fall over just because of a dangling symlink
Previously, the inotify server failed to start if .hg/inotify.sock was
a symlink that pointed to a non-existent path. This behaviour does not
seem to make any sense.
Now, if we encounter a broken symlink, we unlink it and continue.
$ "$TESTDIR/hghave" pyflakes || exit 80
$ cd "`dirname "$TESTDIR"`"
$ pyflakes mercurial hgext 2>&1 | "$TESTDIR/filterpyflakes.py"
hgext/inotify/linux/__init__.py:*: 'from _inotify import *' used; unable to detect undefined names (glob)