JDWP: avoid crash on unsupported modifier
JDWP: avoid crash on unsupported modifier

Returns NOT_IMPLEMENTED error if we receive an event request with an
unsupported modifier.

Bug: https://code.google.com/p/android/issues/detail?id=81037
Bug: 18617787
Change-Id: I97729e2f98af3a75d24604926a89860255d4acae

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst