app/test: increase memory allocated for greedy autotests

app/test: increase memory allocated for greedy autotests

The autotest lists, requirements and distribution needs a big rework
to reduce the amount of cores and memory required.
The root cause is not addressed yet.

This patch just increase some memory allocation for some greedy tests
which often fail because of memory fragmentation:
LPM6 and reentrancy tests in groups 3 and 6 respectively.

Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Tested-by: Olivier Matz <olivier.matz@6wind.com>