DO NOT MERGE Fixed bug in the case of resolution change.

Modified the way i4_header_decoded in decoder context
is used, to ensure that resolution change is detected
even if PPS has not been decoded.

Cherry pick of Change-Id: Ibb3f8dfbeb66a999fd81720a7d2a02dd951a55c4
which went into master post-N.

Bug: 35583675
Test: ran POC, no longer hangs
Change-Id: Ifd21ebe1827d6d0c13018983c46c4301c2bb1669
(cherry picked from commit 8454dbfccd4b558e880596f313d269a9083da86b)