Fix Small Memory Leaks

Found with the configuration running the unit test through valgrind.

    % ./configure CFLAGS=-DNO_WOLFSSL_CIPHER_SUITE_TEST \
      --enable-all --disable-fastmath --enable-debug --disable-shared

1. ssl.c: In wolfSSL_DSA_generate_key(), we initialize (and allocate)
   all the parameters in the key (p, q, g, x, y), and then we generate a
   key, initializes (and allocates) x and y, again. mp_clear them
   first.
2. evp.c: When printing public keys, the temporary mp_int wasn't getting
   correctly freed.
3. evp.c: When printing public keys, modified the utility functions to
   return once with a do-while-0 loop.