5.5 mysqldump.test fails

mysqldump.test fails on few builders.
The new test, added for a bug 12809202, is fundamentally flawed.
It assumes that, when running program 2>&1, lines printed to stderr and stdout, appear in the same order in which they were printed. But as the output is buffered (stdout, at least), this is not the case.

Possible fixed:

• remove the offending test case
• rewrite it to be correct
• fix mysqldump.c to not buffer stdout (the least desirable solution - fixing a perfectly correct program to satisfy invalid test case assumptions)