rsyslog: upgrade to 7.6.1

1. remove two backport patch: 0001-bugfix-potential-abort-during-HUP.patch
and 0001-remove-memleak-introduced-by-GenerateLocalHostName-H.patch
2. update the patch json-0.12-fix.patch
3. remove a obsolete patch rsyslog-use-serial-tests-config-needed-by-ptest.patch
4. update the Dependence
5. update the checksum

Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>