role::cache get rid of unrecognized escape sequences

puppet parser validate is emitting warnings on manifests/role/cache.php
because some escaped regex are in double quotes.  The warning messages
are:

Warning: Unrecognised escape sequence '\1'
Warning: Unrecognised escape sequence '\?'
Warning: Unrecognised escape sequence '\.'

Using single quotes let puppet skip expansion / escaping inside the
string.

Change example:

-"wikimedia\.org"
+'wikimedia\.org'

Change-Id: I103e091d14fac90708f15fac544fa5d2996057bb