Fix performance regression on SVCOMP benchmark suite

```
ldv-consumption/32_7a_cilled_false-unreach-call_linux-3.8-rc1-32_7a-fs--ecryptfs--ecryptfs.ko-ldv_main1_sequence_infinite_withcheck_stateful.cil.out.c_.bpl
snapshot-11-effctclone/merged.yml : FinalResultType.BUG_FOUND (/tmp/pbs.1346865.cx1b/wd/workdir-1270) (444.8166378069727 secs)
snapshot-12/merged.yml : FinalResultType.UNKNOWN (/tmp/pbs.1346866.cx1b/wd/workdir-1270) (900.0 secs)
```
