Fix BaseMetaPipeEntity pass wrong side argument to 'onPlayerAttach'

[reobf]

The argument passed to 'onPlayerAttach' is the clicked side('side'), not the wrenching side('coverSide'), 'onPlayerAttach' will receive wrong argument if attaching cover when sneaking.

This bug has no bad effects for now, because most 'onPlayerAttach' is a no-op for most covers.
And the only one CoverBehavour that overrides 'onPlayerAttach' is metrics cover, which is not allowed to be attched to BaseMetaPipeEntity.
But I think this will help if some CoverBehavour overrides onPlayerAttach in the future.

compare to BaseMetaTileEntity which is implemented correctly:

GT5-Unofficial/src/main/java/gregtech/api/metatileentity/BaseMetaTileEntity.java

Lines 1680 to 1683 in e9fe2d8

	setCoverItemAtSide(coverSide, tCurrentItem);
	coverBehavior.onPlayerAttach(aPlayer, tCurrentItem, this, coverSide);

GT5-Unofficial/src/main/java/gregtech/api/metatileentity/BaseMetaPipeEntity.java

Lines 961 to 964 in e9fe2d8

	setCoverItemAtSide(coverSide, tCurrentItem);
	coverBehavior.onPlayerAttach(aPlayer, tCurrentItem, this, side);