qemu: command: Fix function name in comment
qemu: command: Fix function name in comment

In commit 042c95bd194 qemuBuildStorageSourceChainAttachPrepareBlockdev
was added but the comment for the function mentions
qemuBuildStorageSourceChainAttachPrepareDrive. Fix the mistake.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

nertpinx/libvirt,jardasgit/libvirt,andreabolognani/libvirt,olafhering/libvirt,jfehlig/libvirt,crobinso/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,libvirt/libvirt,crobinso/libvirt,olafhering/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,jardasgit/libvirt,jardasgit/libvirt,zippy2/libvirt,olafhering/libvirt,zippy2/libvirt,andreabolognani/libvirt,nertpinx/libvirt,jardasgit/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,olafhering/libvirt,libvirt/libvirt,nertpinx/libvirt,andreabolognani/libvirt,libvirt/libvirt,crobinso/libvirt