test/common: Don't exit from within the killprocess()

This breaks the flow of EXIT traps that use this function together
with errexit. Consider:

set -e
trap 'killprocess $pid_not_found; nvmftestfini' EXIT
...

if killprocess() suddenly exits the remaining parts of the trap won't
be executed.

Also, if the process is not found, allow killprocess() to return
success - if it's gone then the main goal of the function is already
achieved. If the process terminated abruptly errexit should pick that
up regardless.

Signed-off-by: Michal Berger <michalx.berger@intel.com>
Change-Id: I93c00c2a2da5457affb2ed2b5bf0ebae9c4bf291
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/10853
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

test/common/autotest_common.sh

@@ -813,7 +813,7 @@ function make_filesystem() {
 function killprocess() {
 	# $1 = process pid
 	if [ -z "$1" ]; then
-		exit 1
+		return 1
 	fi
 
 	if kill -0 $1; then
@@ -840,7 +840,6 @@ function killprocess() {
 	else
 		# the process is not there anymore
 		echo "Process with pid $1 is not found"
-		exit 1
 	fi
 }