smb_lockmsghdr() was sleeping because the lock attempt failed (the header was
already locked in smb_addmsg()). So smb_lockmsghdr() will now only sleep if
the unlock() call was successful.
Bugfix in smb_getmsghdr(), msg->total_hfields was incremented before the read
and malloc of hfield_dat, if the read failed, the subsequent call to
smb_freemsgmem() would segfault.