tools: cgconfig/cgrulesengd - skip parsing non .conf files

tools: cgconfig/cgrulesengd - skip parsing non .conf files

Currently, the list of files to be parsed is constructed by reading the
directories passed with '-L' command line option or by cgrulesend from
'/etc/cgconfig.d'.  The directories might also host non-configuration
files, parsing them will result in failure.

Consider the following example:

 # ls /etc/cgconfig.d
 cgconfig-oradb.conf  cgconfig-oradb.conf.rpmsave test .conf e

 # /usr/sbin/cgconfigparser -l /etc/cgconfig.conf -L /etc/cgconfig.d -s 1664
 /usr/sbin/cgconfigparser; error loading /etc/cgconfig.d/cgconfig-oradb.conf.rpmsave:
 Cgroup, the requested group parameter does not exist

fix it by skipping files with non .conf extensions, while building the
list of files to be parsed for cgroup configurations.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>