efi_selftest: check length reported by GetNextVariableName()

GetNextVariableName should report the length of the variable including the
final 0x0000 in bytes.

Check this in the unit test.

Increase the buffer size for variable names. 40 bytes is too short.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
1 file changed