mausezahn: Restore handling of raw hex string passed in on command line

mausezahn: Restore handling of raw hex string passed in on command line

Originally all hex strings (whether they were given on the command line
or in a file) were handled by a call to str2hex():

bytestring_s = str2hex (tx.arg_string, bytestring, MAX_PAYLOAD_SIZE);

Commit f634c74 added code to parse out "payload=" or "p=" flags that may
have been added at the start of the hex string. This code also changed the
logic around this str2hex() call to only call the function and populate
bytestring_s if one of these flags was found. This broke the ability to
pass in a raw hex string on the command line since it fails the check and
bytestring_s is never populated with the hex bytes. I've added an else
condition to make the str2hex() call using the old method in cases where
no "payload=" or "p=" flags are found.

Signed-off-by: Nick Grauel <nicolas.grauel@plexxi.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>