vlog.at: Avoid using GNU sed extension

vlog.at: Avoid using GNU sed extension

BRE alternative (\|) is an GNU sed extension. [1]
It isn't available in NetBSD sed.

[1] http://www.gnu.org/software/sed/manual/sed.html#Regular-Expressions
    regexp1\|regexp2
        Matches either regexp1 or regexp2. Use parentheses to use
        complex alternative regular expressions. The matching process
        tries each alternative in turn, from left to right, and the
        first one that succeeds is used. It is a GNU extension.

Signed-off-by: YAMAMOTO Takashi <yamamoto@midokura.com>
Acked-by: Ben Pfaff <blp@ovn.org>