Widens recoverable failure scenarios for schema indexes

Failures while populating indexes include crashes which may leave the
 index files themselves inconsistent. That may lead to the indexes
 being unable to open and recovery on them impossible to proceed. However,
 such a scenario can be recovered by deleting and repopulating the index,
 as it's done for failures so far.
 This commit adds two more exceptions to the list of recovereable errors.
 FileNotFoundException and EOFException thrown when opening a lucene
 index, which may come up if the index is not closed properly, as in
 the case of a VM crash.
Merge pull request #2012 from digitalstain/index-open-failure-handling

Widens recoverable failure scenarios for schema indexes