tinydtls: call dtls_init() also for the test server
tinydtls: call dtls_init() also for the test server

This call was missing, but it worked somehow with the current code.

Signed-off-by: Hauke Mehrtens <435ddd46dc66c007a1fa20144c823d37e0d23436@hauke-m.de>

nmacs/tinydtls,jvermillard/tinydtls,nmacs/tinydtls,yunus/TinyDTLS-WebID,fvdnabee/tinydtls,fvdnabee/tinydtls,jvermillard/tinydtls,OlegHahm/tinydtls,OlegHahm/tinydtls,nmacs/tinydtls,jvermillard/tinydtls,spark/tinydtls,yunus/TinyDTLS-WebID,thecodemaiden/tinydtls-fork,spark/tinydtls,spark/tinydtls,OlegHahm/tinydtls,fvdnabee/tinydtls,yunus/TinyDTLS-WebID,thecodemaiden/tinydtls-fork,nmacs/tinydtls,thecodemaiden/tinydtls-fork