Changes

dia/diameter_3gpp_ts29_229.dia: inherit only Line-Identifier

That's the only type being used, and skip inheriting other types
avoids inherit problem below:

ETSI ES 283 035  has an AVP (vendor=ETSI) with same name "Event-Type" but
different content (enumerated) and vendor (ETSI) than the one in 3GPP TS
32.299 (grouped, vendor 3GPP).

When trying to inherit one from the other (through indirect TS 29.229),
diameter compiler fails with:
diameter_3gpp_ts32_299.dia failed: AVP Event-Type imported by @inherits diameter_etsi_es283_035 at line 0 defined at line 143

Change-Id: Iece0c768eb2dbb429726796a73274fd476cd1d0b