Fix escaping warnings from puppet

Puppet's double quoted strings warn about unrecognized escapes.  Double
up the backslashes to get literal backslashes for our sed expression.

This should fix the following warnings:

    warning: Unrecognised escape sequence '\+' in file /etc/puppet/modules/line/manifests/init.pp at line 15
    warning: Unrecognised escape sequence '\(' in file /etc/puppet/modules/line/manifests/init.pp at line 20
    warning: Unrecognised escape sequence '\+' in file /etc/puppet/modules/line/manifests/init.pp at line 20
    warning: Unrecognised escape sequence '\)' in file /etc/puppet/modules/line/manifests/init.pp at line 20
    warning: Unrecognised escape sequence '\1' in file /etc/puppet/modules/line/manifests/init.pp at line 20