Fixed build fail issue when building only plugin-firewall

Fixed build fail issue when building only plugin-firewall

Description:
This patch fixes a build fail issue when we try to build only plugin-firewall.

Below is the error which is generated when build fails:-
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[   11s] In file included from /home/abuild/rpmbuild/BUILD/stc-manager-0.0.90/include/stc-manager.h:21:0,
[   11s]                  from /home/abuild/rpmbuild/BUILD/stc-manager-0.0.90/plugin/firewall/include/stc-plugin-firewall.h:30,
[   11s]                  from /home/abuild/rpmbuild/BUILD/stc-manager-0.0.90/plugin/firewall/stc-plugin-firewall.c:17:
[   11s] /home/abuild/rpmbuild/BUILD/stc-manager-0.0.90/include/stc-manager-util.h:21:18: fatal error: glib.h: No such file or directory
[   11s]  #include <glib.h>
[   11s]                   ^
[   11s] compilation terminated.
=======================================================

Change-Id: Id8a01d4ab761c39f9c2bfd1cf3bbfd664e1322b0
Signed-off-by: Nishant Chaprana <n.chaprana@samsung.com>