Add scriptlet-specific disablers for %pretrans and %posttrans

Add scriptlet-specific disablers for %pretrans and %posttrans

- Previously %pretrans and %posttrans were tied to --nopre and --nopost
  disablers (since commit 0b2d7775c5e828652e45829f551352b93890bbc8)
  because back then, there was no room new disablers in rpmtransFlags
  bitfield. This is no longer the case as of rpm >= 4.9.x where
  a bunch of obsolete flags were axed, so we can now add specific
  --nopretrans and --noposttrans switches + corresponding flags.
- This is obviously a behavior change as --nopre and --nopost no
  longer affect %pretrans and %posttrans, but --noscripts behavior
  remains the same.

Change-Id: I7d8ebba44573f0a72a4eecfc8040af86e95409ce