Catch runtime exceptions when parsing DHCP packets

Fix merge conflict into nyc-mr1-security-a-release
This patch adds a try catch all to DHCP packet parsing so that
DhcpClient does not choke on malformed packets, brinding down with it
the whole framework.

Test: added new unit tests catching the issue fixed in this patch.
Bug: 31850211
Change-Id: I3c50a149fed6b2cbc4f40bb4f0e5bb2b56859b44
(cherry picked from commit 1af48bbbabdf276b7e7a5a86b28f67332ae6b04d)