evp_store_test: Compare strings using EXPECT_STREQ
evp_store_test: Compare strings using EXPECT_STREQ

Otherwise we may fail to compare equally if the compiler doesn't
perform string literal canonicalization.

Fixes intermittent failure in highly coverage tests.

Change-Id: Idb9e907b60ebb2569f223ad60ea1e8ccc735160b
Reviewed-on: http://review.couchbase.org/66760
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Will Gardner <cbd6f5d9092d9ef7d5c0510d53bba134b22c02f2@couchbase.com>

membase/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,daverigby/kv_engine,daverigby/ep-engine,couchbase/ep-engine,daverigby/kv_engine,membase/ep-engine,daverigby/kv_engine,daverigby/ep-engine,daverigby/ep-engine,teligent-ru/ep-engine,daverigby/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,daverigby/kv_engine,membase/ep-engine,teligent-ru/ep-engine,membase/ep-engine,couchbase/ep-engine