tests: fix command line overflow on ksh
"<command> `hg manifest`" overflows the puny 1024 byte command line length
limit on AIX default shell ksh. Replace with "hg manifest | xargs <command>".
Welcome to Mercurial for Windows!
---------------------------------
For configuration and usage directions, please read the ReadMe.html
file that comes with this package.
Also check the release notes at:
http://mercurial.selenic.com/wiki/WhatsNew