Makefile: Use the name provided to upload in run
Makefile: Use the name provided to upload in run

This fixes an issue introduced in the split of push and run.
Before this commit, an image could be pushed to a custom location from
the presence of the `CLOUDSDK_IMAGE_NAME` variable. The subsquent run
would fail as the name `test-ltp` or `test` had been hard coded in the
Make target. We now use a target-specific variable which is only set if
there is not an existing variable in the environment

Signed-off-by: Dave Tucker <f7e663289261bf5663f14748dd0817050df83f40@docker.com>

JohnnyLeone/linuxkit,thebsdbox/linuxkit,djs55/linuxkit,konstruktoid/linuxkit,eyz/linuxkit,YuPengZTE/linuxkit,thebsdbox/linuxkit,justincormack/linuxkit,rn/linuxkit,YuPengZTE/linuxkit,thebsdbox/linuxkit,yankcrime/linuxkit,zx2c4/linuxkit,rn/linuxkit,zx2c4/linuxkit,yankcrime/linuxkit,rn/linuxkit,yankcrime/linuxkit,davefreitag/linuxkit,furious-luke/linuxkit,furious-luke/linuxkit,zx2c4/linuxkit,ndauten/linuxkit,mor1/linuxkit,linuxkit/linuxkit,rn/linuxkit,kencochrane/linuxkit,mor1/linuxkit,YuPengZTE/linuxkit,radu-matei/linuxkit,t-koulouris/linuxkit,konstruktoid/linuxkit,eyz/linuxkit,konstruktoid/linuxkit,thebsdbox/linuxkit,davefreitag/linuxkit,ndauten/linuxkit,djs55/linuxkit,eyz/linuxkit,justincormack/linuxkit,linuxkit/linuxkit,linuxkit/linuxkit,ndauten/linuxkit,zx2c4/linuxkit,yankcrime/linuxkit,linuxkit/linuxkit,thebsdbox/linuxkit,YuPengZTE/linuxkit,deitch/linuxkit,kencochrane/linuxkit,mor1/linuxkit,samoht/linuxkit,YuPengZTE/linuxkit,justincormack/linuxkit,davefreitag/linuxkit,deitch/linuxkit,justincormack/linuxkit,JohnnyLeone/linuxkit,deitch/linuxkit,deitch/linuxkit,samoht/linuxkit,t-koulouris/linuxkit,furious-luke/linuxkit,thebsdbox/linuxkit,ndauten/linuxkit,radu-matei/linuxkit,samoht/linuxkit,justincormack/linuxkit,samoht/linuxkit,yankcrime/linuxkit,rn/linuxkit,JohnnyLeone/linuxkit,t-koulouris/linuxkit,kencochrane/linuxkit,davefreitag/linuxkit,konstruktoid/linuxkit,djs55/linuxkit,kencochrane/linuxkit,radu-matei/linuxkit,samoht/linuxkit,mor1/linuxkit,kencochrane/linuxkit,djs55/linuxkit,radu-matei/linuxkit,konstruktoid/linuxkit,t-koulouris/linuxkit,radu-matei/linuxkit,furious-luke/linuxkit,kencochrane/linuxkit,mor1/linuxkit,ndauten/linuxkit,eyz/linuxkit,deitch/linuxkit,JohnnyLeone/linuxkit,t-koulouris/linuxkit,eyz/linuxkit,linuxkit/linuxkit,ndauten/linuxkit,furious-luke/linuxkit,davefreitag/linuxkit,eyz/linuxkit,YuPengZTE/linuxkit,konstruktoid/linuxkit,yankcrime/linuxkit,justincormack/linuxkit,zx2c4/linuxkit,djs55/linuxkit,JohnnyLeone/linuxkit