network: Avoid memory leaks on networkBuildDnsmasqArgv
network: Avoid memory leaks on networkBuildDnsmasqArgv

Detected by valgrind. Leaks introduced in commit 973af236.

* src/network/bridge_driver.c: fix memory leaks on failure and successful path.

* How to reproduce?
% make -C tests check TESTS=networkxml2argvtest
% cd tests && valgrind -v --leak-check=full ./networkxml2argvtest

* Actual result:

==2226== 3 bytes in 1 blocks are definitely lost in loss record 1 of 24
==2226==    at 0x4A05FDE: malloc (vg_replace_malloc.c:236)
==2226==    by 0x39CF0FEDE7: __vasprintf_chk (in /lib64/libc-2.12.so)
==2226==    by 0x41DFF7: virVasprintf (stdio2.h:199)
==2226==    by 0x41E0B7: virAsprintf (util.c:1695)
==2226==    by 0x41A2D9: networkBuildDhcpDaemonCommandLine (bridge_driver.c:545)
==2226==    by 0x4145C8: testCompareXMLToArgvHelper (networkxml2argvtest.c:47)
==2226==    by 0x4156A1: virtTestRun (testutils.c:141)
==2226==    by 0x414332: mymain (networkxml2argvtest.c:123)
==2226==    by 0x414D97: virtTestMain (testutils.c:696)
==2226==    by 0x39CF01ECDC: (below main) (in /lib64/libc-2.12.so)
==2226==
==2226== 3 bytes in 1 blocks are definitely lost in loss record 2 of 24
==2226==    at 0x4A05FDE: malloc (vg_replace_malloc.c:236)
==2226==    by 0x39CF0FEDE7: __vasprintf_chk (in /lib64/libc-2.12.so)
==2226==    by 0x41DFF7: virVasprintf (stdio2.h:199)
==2226==    by 0x41E0B7: virAsprintf (util.c:1695)
==2226==    by 0x41A307: networkBuildDhcpDaemonCommandLine (bridge_driver.c:551)
==2226==    by 0x4145C8: testCompareXMLToArgvHelper (networkxml2argvtest.c:47)
==2226==    by 0x4156A1: virtTestRun (testutils.c:141)
==2226==    by 0x414332: mymain (networkxml2argvtest.c:123)
==2226==    by 0x414D97: virtTestMain (testutils.c:696)
==2226==    by 0x39CF01ECDC: (below main) (in /lib64/libc-2.12.so)
==2226==
==2226== 5 bytes in 1 blocks are definitely lost in loss record 4 of 24
==2226==    at 0x4A05FDE: malloc (vg_replace_malloc.c:236)
==2226==    by 0x39CF0FEDE7: __vasprintf_chk (in /lib64/libc-2.12.so)
==2226==    by 0x41DFF7: virVasprintf (stdio2.h:199)
==2226==    by 0x41E0B7: virAsprintf (util.c:1695)
==2226==    by 0x41A2AB: networkBuildDhcpDaemonCommandLine (bridge_driver.c:539)
==2226==    by 0x4145C8: testCompareXMLToArgvHelper (networkxml2argvtest.c:47)
==2226==    by 0x4156A1: virtTestRun (testutils.c:141)
==2226==    by 0x414332: mymain (networkxml2argvtest.c:123)
==2226==    by 0x414D97: virtTestMain (testutils.c:696)
==2226==    by 0x39CF01ECDC: (below main) (in /lib64/libc-2.12.so)
==2226==
==2226== LEAK SUMMARY:
==2226==    definitely lost: 11 bytes in 3 blocks

Signed-off-by: Alex Jia <e236faec8cb8371bfb245ba3769a84afc9a11438@redhat.com>
Signed-off-by: Eric Blake <a9da18479c871fe903d9590822cfe2629c6a4d11@redhat.com>

rlaager/libvirt,libvirt/libvirt,taget/libvirt,rmarwaha/libvirt1,jardasgit/libvirt,danwent/libvirt-ovs,eskultety/libvirt,trainstack/libvirt,nertpinx/libvirt,iam-TJ/libvirt,wiedi/libvirt,rmarwaha/libvirt1,jfehlig/libvirt,emaste/libvirt,rmarwaha/libvirt1,novel/fbsd-libvirt,shugaoye/libvirt,andreabolognani/libvirt,bjzhang/libvirt,dumbbell/libvirt,novel/fbsd-libvirt,olafhering/libvirt,siboulet/libvirt-openvz,taget/libvirt,fabianfreyer/libvirt,siboulet/libvirt-openvz,bjzhang/libvirt,nertpinx/libvirt,novel/fbsd-libvirt,novel/fbsd-libvirt,libvirt/libvirt,iam-TJ/libvirt,warewolf/libvirt,wiedi/libvirt,trainstack/libvirt,jfehlig/libvirt,crobinso/libvirt,bjzhang/libvirt,foomango/libvirt,trainstack/libvirt,eskultety/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,bjzhang/libvirt,rmarwaha/libvirt,rmarwaha/libvirt,libvirt/libvirt,rlaager/libvirt,warewolf/libvirt,rmarwaha/libvirt,taget/libvirt,warewolf/libvirt,shugaoye/libvirt,iam-TJ/libvirt,warewolf/libvirt,emaste/libvirt,datto/libvirt,jardasgit/libvirt,wiedi/libvirt,crobinso/libvirt,elmarco/libvirt,jfehlig/libvirt,taget/libvirt,siboulet/libvirt-openvz,iam-TJ/libvirt,jardasgit/libvirt,shugaoye/libvirt,crobinso/libvirt,novel/fbsd-libvirt,andreabolognani/libvirt,rmarwaha/libvirt,wiedi/libvirt,rlaager/libvirt,dumbbell/libvirt,zhlcindy/libvirt-1.1.4-maintain,andreabolognani/libvirt,iam-TJ/libvirt,andreabolognani/libvirt,rlaager/libvirt,emaste/libvirt,VenkatDatta/libvirt,shugaoye/libvirt,rlaager/libvirt,zippy2/libvirt,libvirt/libvirt,foomango/libvirt,rmarwaha/libvirt,olafhering/libvirt,eskultety/libvirt,crobinso/libvirt,jeckersb/libvirt,trainstack/libvirt,olafhering/libvirt,warewolf/libvirt,trainstack/libvirt,warewolf/libvirt,datto/libvirt,dumbbell/libvirt,emaste/libvirt,zhlcindy/libvirt-1.1.4-maintain,eskultety/libvirt,nertpinx/libvirt,jardasgit/libvirt,iam-TJ/libvirt,fabianfreyer/libvirt,trainstack/libvirt,olafhering/libvirt,datto/libvirt,wiedi/libvirt,VenkatDatta/libvirt,foomango/libvirt,cbosdo/libvirt,zippy2/libvirt,fabianfreyer/libvirt,dumbbell/libvirt,foomango/libvirt,jeckersb/libvirt,jeckersb/libvirt,taget/libvirt,jardasgit/libvirt,zippy2/libvirt,zhlcindy/libvirt-1.1.4-maintain,bjzhang/libvirt,zhlcindy/libvirt-1.1.4-maintain,cbosdo/libvirt,shugaoye/libvirt,jeckersb/libvirt,jeckersb/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,eskultety/libvirt,rmarwaha/libvirt1,wiedi/libvirt,emaste/libvirt,emaste/libvirt,cbosdo/libvirt,iam-TJ/libvirt,datto/libvirt,novel/fbsd-libvirt,novel/fbsd-libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,siboulet/libvirt-openvz,danwent/libvirt-ovs,jeckersb/libvirt,dumbbell/libvirt,cbosdo/libvirt,trainstack/libvirt,wiedi/libvirt,siboulet/libvirt-openvz,foomango/libvirt,jfehlig/libvirt,elmarco/libvirt,agx/libvirt,fabianfreyer/libvirt,agx/libvirt,emaste/libvirt,danwent/libvirt-ovs,dumbbell/libvirt,rmarwaha/libvirt,zippy2/libvirt,elmarco/libvirt,datto/libvirt,rmarwaha/libvirt1,zhlcindy/libvirt-1.1.4-maintain,VenkatDatta/libvirt,jeckersb/libvirt,elmarco/libvirt,danwent/libvirt-ovs,rmarwaha/libvirt1,agx/libvirt,novel/fbsd-libvirt,agx/libvirt,warewolf/libvirt,agx/libvirt,elmarco/libvirt,cbosdo/libvirt,danwent/libvirt-ovs,novel/fbsd-libvirt