staticd: Fix `make check` failures

staticd: Fix `make check` failures

Recent commit:
abc246e19345cbd2bc74c7dc50dac0b9cf2addf8

Has broken `make check` with recently new compilers:

/usr/bin/ld: staticd/libstatic.a(static_nb_config.o): warning: relocation against `zebra_ecmp_count' in read-only section `.text'
  CCLD     tests/bgpd/test_peer_attr
  CCLD     tests/bgpd/test_packet
/usr/bin/ld: staticd/libstatic.a(static_zebra.o): in function `static_zebra_capabilities':
/home/sharpd/frr5/staticd/static_zebra.c:208: undefined reference to `zebra_ecmp_count'
/usr/bin/ld: staticd/libstatic.a(static_zebra.o): in function `static_zebra_route_add':
/home/sharpd/frr5/staticd/static_zebra.c:418: undefined reference to `zebra_ecmp_count'
/usr/bin/ld: staticd/libstatic.a(static_nb_config.o): in function `static_nexthop_create':
/home/sharpd/frr5/staticd/static_nb_config.c:174: undefined reference to `zebra_ecmp_count'
/usr/bin/ld: /home/sharpd/frr5/staticd/static_nb_config.c:175: undefined reference to `zebra_ecmp_count'
/usr/bin/ld: warning: creating DT_TEXTREL in a PIE
collect2: error: ld returned 1 exit status
make: *** [Makefile:8679: tests/lib/test_grpc] Error 1
make: *** Waiting for unfinished jobs....

Essentially the newly introduced variable zebra_ecmp_count is not available in the
libstatic.a compiled and make check has code that compiles against it.

The fix is to just move the variable to the library.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>