ci: clean up CentOS 7 related tweaks

We have disabled CentOS 7 tests in CI. This patch reverts the
changes introduced in the following commit:

24bc083653
ci: disable some tests on CentOS 7

Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>

test/others/ns_ext/run.sh

@@ -4,8 +4,6 @@ set -x
 
 if [[ "$1" == "pid" ]]; then
 	NS=pid
-	# CentOS 7 kernels do not have NSpid -> skip this test
-	grep NSpid /proc/self/status || exit 0
 else
 	NS=net
 fi

test/others/ns_ext/run_pidns.sh

@@ -2,9 +2,6 @@
 
 set -e
 
-# CentOS 7 kernels do not have NSpid -> skip this test
-grep NSpid /proc/self/status || exit 0
-
 # This test creates a process in non-host pidns and then dumps it and restores
 # it into host pidns. We use pid >100000 in non-host pidns to make sure it does
 # not intersect with some host pid on restore but it is potentially racy so

test/others/rpc/run.sh

@@ -1,14 +1,6 @@
 #!/bin/bash
 
-set -ex
-
-if [ -e /etc/os-release ]; then
-	. /etc/os-release
-	if [ "$ID" == "centos" ] && [[ "$VERSION_ID" == "7"* ]];then
-		echo "Skipping tests on CentOS 7 because they do not work in CI"
-		exit 0
-	fi
-fi
+set -e
 
 CRIU=./criu