Read install session attrs before child elements

As otherwise the ATTR_INSTALL_REASON attribute would be read from the
TAG_GRANTED_RUNTIME_PERMISSION element.

Test: Restarted right after SUW was done and saw apps getting restored
      after reboot.
Change-Id: I53f37d8fee54b3cc2a000971d7244fa47f3509f2
Fixes: 70826795