DR-initiated flush at certain points during function interception can mess up recursion counts

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on August 11, 2011 16:23:58_

now that I put in issue #114 to clear out call_site_table and post_call_table
entries on fragment deletion, a flush (besides our own, which I explicitly
handle) occurring during the dr_redirect_execution could case recursion
counts to get off, leading to the assert in issue #552 .

also, flush between call-site action (i.e., at call and not inside callee)
and entering callee could cause the same problem.

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=553_