Fixed parse escaped value with space at end of string

[stupalov]

Summary

Fixed parsing of escaped .snmprec values that end with a significant space character. The parser used to strip the whole record before splitting fields, so a trailing space in the value field was lost before escaped value evaluation.

Problem

For some escaped values, snmpsim fails with an error like:

ERROR data error at loadmaster.snmprec controller for 1.3.6.1.2.1.3.1.1.3.3.1.85.209.202.31: value evaluation error for tag `64`, value [85, 209, 202]: Bad IP address syntax

For example, this request returns an IP address whose last byte can be encoded as a trailing space in the escaped .snmprec value:

$ snmpwalk -v2c -c community -Pu -M ../rfc:../net-snmp:. -m ALL hostname .1.3.6.1.2.1.3.1.1.3.3.1
RFC1213-MIB::atNetAddress.3.1.85.209.202.31 = Network Address: 55:D1:CA:1F
RFC1213-MIB::atNetAddress.3.1.85.209.202.31 = No more variables left in this MIB View (It is past the end of the MIB tree)

Relevant part of loadmaster.snmprec:

1.3.6.1.2.1.3.1.1.3.3.1.85.209.202.31|64e|U\xd1\xca\x1f
1.3.6.1.2.1.3.1.1.3.3.1.85.209.202.32|64e|U\xd1\xca 

In the last line, the space at the end of the value is significant and should be converted to number 32. This change trims only OID/tag whitespace and record terminators from the value, preserving the trailing value space.

Tests

.venv/bin/python -B -m pytest tests

Result: 2 passed, 5 skipped.

Ported from stupalov@a1275f9

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