fetch2/npm: explicitly specify workdir

fetch2/npm: explicitly specify workdir

We were downloading into the current directory here, which is fine if
that current directory can be expected to be the right place - but
that's not true when called from recipetool within OE. We should
explicitly specify the directory to run the command in and then there
won't be a problem.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>