ipk: Import re in manifest module

```
File: '/home/andrew/src/openbmc/openbmc/meta/lib/oe/package_manager/ipk/manifest.py', lineno: 67, function: create_full
     0063:
     0064:        output = pm.dummy_install(pkgs_to_install)
     0065:
     0066:        with open(self.full_manifest, 'w+') as manifest:
 *** 0067:            pkg_re = re.compile('^Installing ([^ ]+) [^ ].*')
     0068:            for line in set(output.split('\n')):
     0069:                m = pkg_re.match(line)
     0070:                if m:
     0071:                    manifest.write(m.group(1) + '\n')
Exception: NameError: name 're' is not defined
```

Change-Id: I769a2ab5e57c7b60598ea0390b576d707356db9d
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>