Fix the cipher decision scheme for export ciphers: the export bits are *not*

Fix the cipher decision scheme for export ciphers: the export bits are *not*
within SSL_MKEY_MASK or SSL_AUTH_MASK, they are within SSL_EXP_MASK.  So, the
original variable has to be used instead of the already masked variable.

Submitted by: Richard Levitte <levitte@stacken.kth.se>
Reviewed by: Ralf S. Engelschall