package_rpm: DEPLOY_DIR_RPM must exist before make index
There is a package-index.bb which will update the index, but the
DEPLOY_DIR_RPM may not exist, for example, when "bitbake package-index"
in a fresh build.
Only the package_rpm.bbclass needs this, the package_ipk.bbclass and
package_deb.bbclass doesn't need.
[YOCTO #2753]
Signed-off-by: Robert Yang <liezhi.yang@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
