8137099: G1 needs to "upgrade" GC within the safepoint if it can't allocate during that safepoint to avoid OoME Summary: During a minor GC, if memory allocation fails, start a full GC within the same VM operation in the same safepoint. This avoids a race where the GC locker can prevent the full GC from occurring, and a premature OoME. Reviewed-by: ehelin, sjohanss, phh Contributed-by: thomas.schatzl@oracle.com, axel.siebenborn@sap.com