package/nodejs: force the use of python2

package/nodejs: force the use of python2

Remove the patches to use a python variable and instead force python2
into the PATH.

Upstream the python variable was recently removed
(see https://github.com/nodejs/node/commit/c3e50ca) and due to dependencies
directly calling python there is a reluctance to change this.  Instead it
is recommended to add python2 into PATH as the nodejs build machines do
(see https://github.com/nodejs/node/issues/418 and
https://github.com/nodejs/node/issues/2735).

Signed-off-by: Martin Bark <martin@barkynet.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>