package_rpm.bbclass: Refactor the attempt only install

package_rpm.bbclass: Refactor the attempt only install

Smart does not have a method to perform an install, but ignore failures.

There was a class of failures that stopped Smart from processing
attemptonly installs.  To work around this we need to iterate over the to
be attempted list.

(From OE-Core rev: 7c11ab93242ad3453b730da79a641479de588227)

Signed-off-by: Mark Hatle <mark.hatle@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>