cmd/pprof: don't use local symbolization for remote source
cmd/pprof: don't use local symbolization for remote source

If we are using a remote source (a URL), and the user did not specify
the executable file to use, then don't try to use a local source.
This was misbehaving because the local symbolizer will not fail
if there is any memory map available, but the presence of a memory map
does not ensure that the files and symbols are actually available.

We still need a pprof testsuite.

Fixes #16159.

Change-Id: I0250082a4d5181c7babc7eeec6bc95b2f3bcaec9
Reviewed-on: https://go-review.googlesource.com/24464
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Joe Tsai <7277d7402195d5c2006c89f45718cf82bb3e527f@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

ImJasonH/go,nawawi/go,derekmarcotte/go,akutz/go,golang/go,polyverse-security/go,vsekhar/elastic-go,polyverse-security/go,golang/go,momchil-velikov/go,Cofyc/go,codestation/go,polyverse-security/go,ImJasonH/go,CAFxX/go,linux-on-ibm-z/go,josharian/go,cloudflare/go,Cofyc/go,akutz/go,suncycheng/go,suncycheng/go,momchil-velikov/go,codestation/go,Cofyc/go,momchil-velikov/go,suncycheng/go,golang/go,goodlang/good,momchil-velikov/go,suncycheng/go,momchil-velikov/go,vsekhar/elastic-go,derekmarcotte/go,goodlang/good,CAFxX/go,josharian/go,CAFxX/go,4ad/go,ImJasonH/go,akutz/go,goodlang/good,Cofyc/go,derekmarcotte/go,akutz/go,codestation/go,momchil-velikov/go,vsekhar/elastic-go,vsekhar/elastic-go,golang/go,polyverse-security/go,goodlang/good,4ad/go,derekmarcotte/go,CAFxX/go,linux-on-ibm-z/go,golang/go,nawawi/go,linux-on-ibm-z/go,polyverse-security/go,goodlang/good,vsekhar/elastic-go,ImJasonH/go,goodlang/good,cloudflare/go,CAFxX/go,4ad/go,josharian/go,derekmarcotte/go,nawawi/go,nawawi/go,ImJasonH/go,4ad/go,golang/go,golang/go,codestation/go,momchil-velikov/go,4ad/go,suncycheng/go,ImJasonH/go,CAFxX/go,polyverse-security/go,christopher-henderson/Go,vsekhar/elastic-go,vsekhar/elastic-go,akutz/go,Cofyc/go,josharian/go,cloudflare/go,momchil-velikov/go,cloudflare/go,derekmarcotte/go,4ad/go,linux-on-ibm-z/go,suncycheng/go,linux-on-ibm-z/go,polyverse-security/go,cloudflare/go,ImJasonH/go,golang/go,cloudflare/go,codestation/go,nawawi/go,codestation/go,akutz/go,josharian/go,vsekhar/elastic-go,linux-on-ibm-z/go,cloudflare/go,codestation/go,linux-on-ibm-z/go,4ad/go,josharian/go,nawawi/go,linux-on-ibm-z/go,josharian/go,derekmarcotte/go,cloudflare/go,goodlang/good,polyverse-security/go,4ad/go,suncycheng/go,akutz/go,suncycheng/go,Cofyc/go,akutz/go,Cofyc/go,derekmarcotte/go,ImJasonH/go,goodlang/good,Cofyc/go,josharian/go,nawawi/go,CAFxX/go,nawawi/go,CAFxX/go,codestation/go