Revert "Revert "utilities/ovs-ctl: Force removal of ip_gre/gre""

Revert "Revert "utilities/ovs-ctl: Force removal of ip_gre/gre""

This reverts commit a94f9524dbc11c78c83d1a49959497f5e73bf949.

This is a revert of a previously reverted commit
2bdd1f3d96a86bea6bdb8788f23ec7dd99b289e3.

When we originally added commit 2bdd1f3d96 it was part of an
effort to work around gre module conflicts found while enabling
the ERSPAN feature. Testing at the time did not show any benefit
so in commit a94f9524db we reverted it.  However, further
developments showed that in some corner cases it did have a
benefit and it did not do any harm so we reverted the original
revert to restore the code.

Signed-off-by: Greg Rose <roseg@vmware.com>
Tested-by: Yifeng Sun <pkusunyifeng@gmail.com>
Reviewed-by: Yifeng Sun <pkusunyifeng@gmail.com>
Signed-off-by: Justin Pettit <jpettit@ovn.org>