v2v: linux: Fix uninstallation of kmod-xenpv from /etc/rc.local script.

In the original conversion of virt-v2v from Perl
(commit 0131d6f666), the Perl regular
expression was incorrectly transscribed.  ‘\b’ was not converted to
‘\\b’ so the new regexp was looking for an ASCII BEL character, not a
word boundary.  Also ‘|’ was used, but Str requires ‘\|’ (ie. "\\|"
in the final source).

To fix these problems I converted the code to use PCRE, and went back
to the original virt-v2v code (virt-v2v.git:
lib/Sys/VirtConvert/Converter/Linux.pm) to find out what the Perl
regular expression should have been.

Note I have also removed ‘.*’ at the beginning and end of the regexp
because PCRE regexps are not anchored.

v2v/convert_linux.ml

@@ -173,10 +173,10 @@ let convert (g : G.guestfs) inspect source output rcaps =
       (try
          let lines = g#read_lines "/etc/rc.local" in
          let lines = Array.to_list lines in
-         let rex = Str.regexp ".*\\b\\(insmod|modprobe\\)\b.*\\bxen-vbd.*" in
+         let rex = PCRE.compile "\\b(insmod|modprobe)\\b.*\\bxen-vbd" in
          let lines = List.map (
            fun s ->
-             if Str.string_match rex s 0 then
+             if PCRE.matches rex s then
                "#" ^ s
              else
                s