Fix wgt, hybrid installer issues

Fix wgt, hybrid installer issues

- Signature will not be saved on requests listed below :
  Hybrid - ManifestPartialInstall, ManifestPartialUpdate
  Wgt - ReadonlyUpdateUninstall, ManifestPartialInstall,
        ManifestPartialInstall, ManifestPartialUpdate
- Change security-related steps from
  StepUpdateSecurity to StepRegisterSecurity
  for some install requests to not trying registration on readonly files
  when partial-rw option has given.

Change-Id: Id0ebad383cbfd2dab6539fff2ba85bf2971a287d
Signed-off-by: Junghyun Yeon <jungh.yeon@samsung.com>