new pkg_add library check breaks pkg_add -u

[Greg Troxel <gdt%lexort.com@localhost>]

pkg_add has been checking that shared libraries are in order, which is
basically good.

But, when using pkg_add -u, it seems to do this after removing the old
package, and then when it errors out, the new package is not installed.
And thus the libraries it provided that other packages are relying on
are missing, and the integrity constraint it tried to ensure is
violated.

In this case, there seems to have been something wrong with a new geos
package.  (Notably, it was not caught by PKG_DEVELOPER, and separately I
don't think it's ok for pkg_add to object to packages that PKG_DEVELOPER
approved.)

(I suspect the geos build somehow picks up a reference to the installed
previous version's library: that's a bug and it's good that was
surfaced.)

After "pkg_add -u" called by make replace errored out, the system was
broken:

  pkg_admin: Dependency geos>=3.3.4 of gdal-lib-3.9.0nb2 unresolved
  pkg_admin: Dependency geos>=3.3.4 of librttopo-1.1.0 unresolved
  pkg_admin: Dependency geos>=3.3.4 of libspatialite-5.1.0nb3 unresolved
  pkg_admin: Dependency geos>=3.6 of postgresql12-postgis-3.4.2nb7 unresolved


I think this should be fixable by running the checks before uninstalling
the old package.