tcap: Support TID with length 1..4
As described in ITU Q.773 4.2.1.3:
"The length of a Transaction ID is 1 to 4 octets."
asn.1 files also describe TIDs the following way:
OrigTransactionID ::= [APPLICATION 8] IMPLICIT OCTET STRING (SIZE (1..4) )
DestTransactionID ::=[APPLICATION 9] IMPLICIT OCTET STRING (SIZE (1..4) )
Take the chance to avoid asserting based on received external input msg.
Related: SYS#5423
Change-Id: I2748d85624e4be708f7554ee3e60a5bda9162845
