Avoid badmatch when getting fabric timeout

[jiangphcn]

Overview

Avoid badmatch when putting _set_purge_infos_limit and getting fabric timeout

Testing recommendations

======================== EUnit ========================
module 'chttpd_purge_tests'
  chttpd db tests
Application crypto was left running!
    chttpd_purge_tests:87: test_empty_purge_request...[0.009 s] ok
    chttpd_purge_tests:104: test_ok_purge_request...[0.285 s] ok
    chttpd_purge_tests:141: test_accepted_purge_request...[0.123 s] ok
    chttpd_purge_tests:173: test_partial_purge_request...[0.084 s] ok
    chttpd_purge_tests:209: test_mixed_purge_request...[0.172 s] ok
    chttpd_purge_tests:257: test_overmany_ids_or_revs_purge_request...[0.130 s] ok
    chttpd_purge_tests:307: test_exceed_limits_on_purge_infos...[0.140 s] ok
    chttpd_purge_tests:350: should_error_set_purged_docs_limit_to0...[0.004 s] ok
    chttpd_purge_tests:358: test_timeout_set_purged_infos_limit...[0.087 s] ok
[os_mon] cpu supervisor port (cpu_sup): Erlang has closed
    [done in 3.567 s]
  [done in 5.743 s]
=======================================================
  All 9 tests passed.

Related Issues or Pull Requests

COUCHDB-3326

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes;

[davisp]

+1