misc/ios: always kill lldb process when it hangs
misc/ios: always kill lldb process when it hangs

The lldb child process is killed if a test runs too long. Also
kill it when the setup times out (and is retried).

Might help with builder flakes where all 5 attempts to start up
lldb fail even though the tests before and after the timeouts
succeed. For example:

...
ok  	vendor/golang_org/x/net/route	37.797s
lldb setup error: command timeout (lldb start for 17s)
start timeout, trying again
lldb setup error: command timeout (lldb start for 17s)
start timeout, trying again
lldb setup error: command timeout (lldb start for 17s)
start timeout, trying again
lldb setup error: command timeout (lldb start for 17s)
start timeout, trying again
lldb setup error: command timeout (lldb start for 17s)
go_darwin_arm_exec: failed to start test harness (retry attempted)
FAIL	vendor/golang_org/x/text/transform	115.185s
ok  	vendor/golang_org/x/text/unicode/norm	122.773s
...

Change-Id: I6638860522896491dccfa12f1e520c0f23df6d66
Reviewed-on: https://go-review.googlesource.com/67791
Run-TryBot: Elias Naur <993af7099cb24ce1a88d64108ae1e8b0385f2fc0@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

polyverse-security/go,codestation/go,Cofyc/go,Cofyc/go,cloudflare/go,cloudflare/go,golang/go,cloudflare/go,nawawi/go,CAFxX/go,josharian/go,CAFxX/go,codestation/go,Cofyc/go,codestation/go,akutz/go,polyverse-security/go,josharian/go,akutz/go,golang/go,nawawi/go,CAFxX/go,nawawi/go,josharian/go,polyverse-security/go,Cofyc/go,cloudflare/go,cloudflare/go,nawawi/go,josharian/go,CAFxX/go,nawawi/go,codestation/go,josharian/go,Cofyc/go,golang/go,golang/go,CAFxX/go,josharian/go,akutz/go,christopher-henderson/Go,josharian/go,golang/go,Cofyc/go,Cofyc/go,akutz/go,josharian/go,golang/go,codestation/go,codestation/go,akutz/go,polyverse-security/go,nawawi/go,CAFxX/go,polyverse-security/go,nawawi/go,codestation/go,polyverse-security/go,golang/go,CAFxX/go,golang/go,cloudflare/go,akutz/go,nawawi/go,codestation/go,akutz/go,polyverse-security/go,polyverse-security/go,cloudflare/go,Cofyc/go,akutz/go,CAFxX/go,cloudflare/go