license: fix for corrupted licensing packets

license: fix for corrupted licensing packets

Since commit a228952 FreeRDP generates corrupt licensing packets if the rdp
security layer is used and the peer did not indicate that it is capable of
processing encrypted licensing packets:
That commit changed rdp->sec_flags after the rdp stream was already initialized
with encryption enabled which placed the PDU payload at an incorrect offset.

Instead of directly modifying the rdp->sec_flags this patch temporarily
disables rdp->do_crypt during rdp stream initialization if the client has not
advertised support for encrypted licensing packets.