http: follow up to r1686271, also needed in 2.4.x/2.2.x by r1686271/r1687339.

Handle reentrance of state BODY_CHUNK_CR to avoid AH02901 when we eat BWS
from multiple reads.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1688536 13f79535-47bb-0310-9956-ffa450edef68