Make get_enterprise_id more flexible when parsing sysObjectID values

[lunkwill42]

Although #2566 was fixed, there is still the unsolved problem that some installations may still have "broken" sysObjectID values in the NetboxType table.

There are actually two duplicate implementations of get_enterprise_id() - one for models.Netbox and one for shadows.Netbox. Only the first is mentioned in #2566, but both should be fixed:

          This method explicitly only checks for a non-dotted enterprise prefix:

nav/python/nav/models/manage.py

Lines 1278 to 1291 in 97fc362

	def get_enterprise_id(self):
	"""Returns the type's enterprise ID as an integer.
	The type's sysobjectid should always start with
	SNMPv2-SMI::enterprises (1.3.6.1.4.1). The next OID element will be
	an enterprise ID, while the remaining elements will describe the type
	specific to the vendor.
	"""
	prefix = u"1.3.6.1.4.1."
	if self.sysobjectid.startswith(prefix):
	specific = self.sysobjectid[len(prefix) :]
	enterprise = specific.split('.')[0]
	return int(enterprise)

Originally posted by @lunkwill42 in #2566 (comment)

[lunkwill42]

An improved version of these methods should use the nav.oids.OID class for OID comparisons and prefix tests..

[hmpf]

If there are bogus data in the database we should probably fix it in the database as well, for consistency.

[lunkwill42]

If there are bogus data in the database we should probably fix it in the database as well, for consistency.

We did discuss that, but the data itself isn't really bogus - it's just that parts of NAV were very picky about the formatting of the string (it did not accept data with a leading ., even though that is the most common way to write out an OID).

#2658 fixes this so that even said "bogus" data would be parsed just fine.