Fix ./jstests/replsets/initial_sync_drop_collection.js to prevent using stale heartbeat info in the test.

_waitForIndicator function in ./src/mongo/shell/replsettest.js always executes the "replSetGetStatus" cmd on primary and gets the member node's state. If the primary is not holding up-to-date info about the replica set members, then replTest.waitForState in finishTest can work incorrectly and lead to failures like in BF-9682.

Fix is to make the setupTest function to wait till secondary node's state reaches "STARTUP2" after its restart.