Fix RPM self-destruction in Dockerfile

Commit 08e30d8 dropped the removal of
rpm-plugin-ima since it no longer was pulled in by default, however that
(no longer?) is the case, due to ima-evm-utils-devel that requires it.

The plugin also pulled in rpm-sign-libs, which could then cause a false
positive in the "rpm library version" test in "make check" if the local
build was configured with the /usr prefix.

(cherry picked from commit 524084c)

Author: dmnks

tests/Dockerfile.fedora

@@ -83,7 +83,9 @@ RUN ln -sf $(rpm --eval '%{_target_platform}%{?_gnu}')-pkg-config \
 RUN rpm -e --nodeps --nodb \
 	rpm \
 	rpm-libs \
-	rpm-build-libs
+	rpm-sign-libs \
+	rpm-build-libs \
+	rpm-plugin-ima
 
 WORKDIR /
 CMD /bin/bash