Coverity fixes - 12023, 12024, and 12025
. 12023 - Ignoring number of bytes read
The return value from fread was ignored and not used for copying
the read content from buffer to mctx.attrplFileContent.
. 12024 - Resource leak
When an error occurred, filter_attr_value was not freed.
. 12025 - Wrong sizeof argument
prfinfo is declared as PRFileInfo64, but when initializing the
structure with NULL, the specified size was for PRFileInfo.
Reviewed by rmeggins (Thank you, Rich!!)
(cherry picked from commit f702868012ac1f9deb1cb92d51cdfd793353e836)
(cherry picked from commit 99f7b65e4bd35ce5d2c24a05178cfca4a44645db)